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PoisonedRefresh: A Fileless Linux Rootkit That Injects PHP Web Shells Into F5 BIG-IP APM Server Memory
Sophos details PoisonedRefresh, a fileless Linux rootkit that injects a memory-resident PHP web shell into F5 BIG-IP APM after exploitation of CVE-2025-53521.
On September 8, 2026, SophosLabs published an analysis of Linux/Agnt-IC (dubbed PoisonedRefresh by ESET) found in compromised F5 BIG-IP Access Policy Manager environments. Initial access leverages CVE-2025-53521, an unauthenticated RCE in BIG-IP APM when an access policy is configured on a virtual server; F5 confirmed exploitation and links the activity to cluster c05d5254, while Shadowserver observed 795 exposed vulnerable endpoints. A first stage hidden in a modified umount binary modifies /usr/sbin/httpd and SELinux configuration and embeds itself in BIG-IP upgrade images for persistence. The second-stage ELF intercepts __libc_start_main, hooks apr_dso_load, and injects a PHP web shell into libphp memory via mmap manipulation, leaving no disk artifacts, and exposes a /bin/bash shell via a local UNIX domain socket instead of a TCP port.
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Hackers Actively Exploit Critical WooCommerce Plugin Vulnerability to Upload PHP Backdoors
Attackers actively exploit CVE-2026-27540 (CVSS 9.8) in WooCommerce Wholesale Lead Capture plugin to upload PHP webshells; patch shipped in version 2.0.3.2.
CVE-2026-27540 (CVSS 9.8) in the WooCommerce Wholesale Lead Capture plugin affects versions 2.0.3.1 and earlier across roughly 6,000 active installations. The unauthenticated AJAX handler wwlc_file_upload_handler trusts a client-supplied file_settings allowlist, letting attackers upload shell.php for remote code execution. Wordfence has blocked more than 100,000 exploit attempts since disclosure, with spikes in June, July, and August 2026. The vendor fixed the flaw in version 2.0.3.2.
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F5 BIG-IP APM Malware Injects a PHP Web Shell Into Memory, Evading Disk Scans
Sophos found F5 BIG-IP APM malware that injects a PHP web shell into Apache's memory, evading disk scans, linked to exploited CVE-2025-53521.
Sophos's September 7 analysis describes malware tied to F5's c05d5254 activity that hooks apr_dso_load, modifies the libphp PHP module in memory, and injects a PHP web shell when Apache loads apm_css.php3, full_wt.php3 or webtop_popup_css.php3, leaving on-disk files clean. A separate installer infects /usr/sbin/httpd and umount, runs before Apache starts, disables SELinux (per ESET's related PoisonedRefresh analysis), and opens a local socket at /run/bigtlog.pipe for shell access. The activity is linked to CVE-2025-53521 in BIG-IP APM, rated 9.8 CVSS 3.1, patched in October 2025, added to CISA KEV on March 27, 2026.
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Stealth rootkit targeting F5 BIG-IP could expose enterprise identity gateways
Sophos analyzed a stealth Linux rootkit that hides a web shell in memory on compromised F5 BIG-IP APM identity gateways, evading file-based detection.
Sophos analyzed a second-stage Linux rootkit implant found in compromised F5 BIG-IP APM environments running Apache and PHP, linked to exploitation of CVE-2025-53521, an unauthenticated RCE. The implant hooks Apache's PHP-loading process and serves modified in-memory versions of three legitimate webtop PHP files (apm_css.php3, full_wt.php3, webtop_popup_css.php3), leaving on-disk files untouched so hashes and integrity checks pass. It also establishes access via an authenticated local UNIX socket that can provide an interactive /bin/bash session. Experts warn compromised APM appliances, which handle federated SSO and terminate TLS at enterprise perimeters, could enable SSO token theft and lateral movement to trusted downstream applications.
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Critical GiveWP Flaw Lets Attackers Run Commands on WordPress Servers
Critical unauthenticated PHP object injection (CVE-2026-82222) in the GiveWP WordPress donation plugin chains to remote code execution; version 4.16.7.2 fixes it.
Patchstack disclosed CVE-2026-82222 (CVSS 10.0), an unauthenticated PHP object injection in GiveWP versions through 4.16.7.1 that chains through TCPDF and Give\TestData gadget classes to arbitrary OS command execution as the web server user. On versions 4.16.5.1 and below, a default installation with one published donation form is enough to exploit, with no user interaction required. Version 4.16.7.2 blocks unsafe serialized data, hardens the gadget chain and cleans already-stored database records; a separate registration bypass issue remains unresolved.
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Elementor Pro Flaw Could Let Unauthenticated Attackers Upload PHP and Execute Code
Patchstack disclosed CVE-2026-32475 (CVSS 9.0), an unauthenticated file-upload flaw in Elementor Pro enabling PHP upload and RCE; fixed in version 4.2.2.
Patchstack researcher Tin Pham reported an unrestricted file upload flaw in Elementor Pro's Forms module (CVE-2026-32475, CVSS 9.0), affecting all versions up to and including 4.2.1. Submitting two file parts for one field bypasses the extension blocklist and writes attacker-controlled PHP into a public uploads directory, yielding unauthenticated remote code execution when a published Elementor page uses a Form widget with a File Upload field. A patched version 4.2.2 shipped August 19, 2026, a day after WordPress 7.0.4 fixed CVE-2026-65640 (CVSS 8.8), an RCE via Postscript file upload when Imagick and Ghostscript are in use.
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Hackers breach F5 BIG-IP APM devices to deploy Linux rootkit
Sophos analyzed a Linux rootkit on F5 BIG-IP APM devices that injects a fileless PHP web shell, likely after CVE-2025-53521 exploitation.
Sophos analyzed a Linux rootkit targeting F5 BIG-IP APM environments, also tracked by ESET as PoisonedRefresh, which hijacks Apache's apr_dso_load module loader to inject a fileless PHP web shell into memory. The implant intercepts __libc_start_main, hides strings with RC4, creates a password-protected local UNIX socket backdoor for interactive Bash access, and persists across BIG-IP upgrade images while modifying SELinux configuration. It is likely a second-stage payload following exploitation of CVE-2025-53521, a critical RCE flaw F5 reclassified from a DoS issue in March. The ShadowServer Foundation tracked 795 F5 BIG-IP APM endpoints exposed online.
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Over 440,000 Exploit Attempts Target Super Forms and Elementor Pro RCE Flaws
Wordfence blocked 440,000+ exploit attempts against critical unauthenticated RCE flaws in WordPress plugins Super Forms and Elementor Pro.
Wordfence reports mass exploitation of two unauthenticated arbitrary file upload RCE flaws: CVE-2026-14894 in Super Forms (CVSS 9.8, fixed in 6.3.314) and CVE-2026-32475 in Elementor Pro (CVSS 9.0/9.8, fixed in 4.2.2), with over 250,000 and 190,000 blocked exploit attempts respectively. Attackers upload Base64-encoded PHP web shells such as Mushr00w_upl.php to execute code, create administrator accounts, exfiltrate data, or seize sites. Super Forms exploitation began July 14, 2026 and peaked above 40,000 requests on August 18; Elementor Pro attacks started August 19. Successful Elementor Pro exploitation requires a published page with a Form widget containing a File Upload field.
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Forminator WordPress Flaw Can Enable Unauthenticated RCE via Malicious PHP Uploads
Wordfence disclosed CVE-2026-15748, a critical unauthenticated file upload flaw enabling RCE in the Forminator Forms WordPress plugin, patched in version 1.56.2.
Wordfence reported CVE-2026-15748 (CVSS 9.8) in Forminator Forms, a WordPress plugin with over 600,000 active installations, allowing unauthenticated attackers to upload arbitrary PHP files and achieve remote code execution. The flaw stems from insufficient file type validation in the handle_file_upload() function, and exploitation requires a form containing both a File Upload field and a Select field, plus a custom upload storage root lacking .htaccess PHP protection. All versions up to and including 1.56.1 are affected; version 1.56.2 released July 31, 2026 fixes the issue. Wordfence also disclosed CVE-2026-15826 (CVSS 9.8), an authentication bypass in User Profile Builder (40,000+ installs) letting unauthenticated attackers log in as administrator, fixed in version 3.16.5 on July 16, 2026.
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Hackers deploy Linux rootkit on F5 BIG-IP APM devices, hiding web shell in memory
Sophos analyzed a Linux rootkit, tracked as PoisonedRefresh, on hacked F5 BIG-IP APM devices hiding an in-memory web shell linked to exploited CVE-2025-53521.
Sophos and ESET analyzed an implant (named PoisonedRefresh by ESET) deployed on compromised F5 BIG-IP APM appliances, which serves enterprise, financial, government, and public sector deployments. The second-stage payload intercepts __libc_start_main, hooks Apache's APR module loader (apr_dso_load), RC4-encodes key strings, and rewrites PHP file reads in memory to embed a web shell inside legitimate scripts like apm_css.php3, full_wt.php3, and webtop_popup_css.php3, leaving on-disk files unchanged. A related installer component infects /usr/sbin/httpd, persists across BIG-IP upgrade images, modifies SELinux configuration, and deploys the payload. The malware also creates a Unix domain socket at /run/bigtlog.pipe that hands authenticated local connections to /bin/bash; F5 links the activity to CVE-2025-53521, an unauthenticated RCE in BIG-IP APM already exploited in the wild.
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WordPress Events Calendar Vulnerabilities Let Hackers Take Over 600,000 Websites
Two unauthenticated RCE flaws (CVSS 9.8) in The Events Calendar WordPress plugin threaten 600,000 sites; patched in 6.17.4.1.
Wordfence Argus disclosed two critical unauthenticated vulnerability chains in The Events Calendar WordPress plugin, tracked as CVE-2026-78006 and CVE-2026-78159, both scoring 9.8 CVSS. CVE-2026-78006 enables PHP object injection leading to RCE via a Lazy_Post_Collection gadget chain, while CVE-2026-78159 abuses Element_Classes::parse_array() to invoke wp_update_user() and reset the admin password. Exploitation works by injecting wp:legacy-widget Gutenberg markup through comments, using WordPress's moderation-preview hash to trigger the block before approval. StellarWP patched both flaws in version 6.17.4.1 after Wordfence's August 2026 disclosure.
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StopAndProtect Uses Nearly 2,000 Hacked WordPress Sites to Spread Malware and Steal Data
Check Point details StopAndProtect: ~2,000 compromised WordPress sites deliver ClickFix fake-CAPTCHA malware toolkit combining ransomware, credential theft, screenshots, and WhatsApp surveillance.
Check Point researcher Jaromír Hořejší reports the campaign begins with ClickFix fake-CAPTCHA prompts that trigger a PowerShell command, then two .NET downloader stages that launch six components: SilentEncryptor, NetworkShareScanner, a VBS spreader, LockScreen, SimpleChatProxy, and SilentDataCollector. Hacked WordPress sites host malware stages, serve C2 commands, and receive exfiltrated logs; the actors installed a self-deleting WordPress plugin enabling arbitrary PHP upload anywhere under the WordPress root. From mid-May to late July 2026 the operators exfiltrated more than 700 archives including screenshots every 30 seconds, keylogger output, and WhatsApp contact data, and opsec failures exposed their Visual Basic automation tooling and lists of nearly 2,000 compromised domains.
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Threat actors started exploiting Juniper flaws shortly after PoC release
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Amasty patches dozens of Magento extensions, 2 critical
Amasty patched dozens of Magento/Adobe Commerce extensions, including two critical flaws allowing unauthenticated web shell upload and remote code execution.
Extension vendor Amasty released fixes for a large batch of Magento and Adobe Commerce modules, with critical unauthenticated file upload flaws in Advanced Product Reviews and Gift Card that allow attackers to plant web shells and take full control of stores. Dozens of additional high-, medium- and low-severity extensions were also patched. The vendor says the release affects almost every Magento and Adobe Commerce store. A related Order Attributes flaw was previously exploited heavily, with Sansec Shield blocking over 12,000 attempts against 25% of Magento stores in three days.
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Unpatched Kaltura mwEmbed Flaws Could Let Remote Attackers Read Files and Run Code
CERT/CC disclosed unpatched Kaltura mwEmbed flaws CVE-2026-19913 and CVE-2026-19912 allowing unauthenticated file reads and remote code execution.
CERT/CC disclosed two unpatched flaws in Kaltura's mwEmbed HTML5 player library, both rooted in unsafe deserialization in mwEmbedLoader.php and exploitable without authentication. CVE-2026-19913 (reporter-scored 9.1) reflects local file contents back via the ServiceUrl parameter, exposing secrets in local.ini; CVE-2026-19912 (reporter-scored 10.0) achieves PHP code execution by writing attacker-controlled objects into web-accessible directories via the uiconf_id parameter. No patch exists and CERT/CC could not reach Kaltura; affected releases include html5lib v2.45, v2.103 and earlier, with the shared multi-tenant CDN hosts also impacted. No exploitation or KEV listing was reported as of August 25, 2026.
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Thai Broadband Provider Hacked via Fortinet Vulnerability
Hackers exploited Fortinet CVE-2024-21762 RCE to breach Thai broadband provider 3BB, deploying MeshCentral backdoors and credential-harvesting tools across its network.
Hunt.io uncovered an intrusion staging directory in Thailand containing 298 files of custom tooling built for Triple T Broadband (3BB) and its former owner Jasmine. Initial access came via fingerprinting a FortiGate SSL-VPN appliance and exploiting CVE-2024-21762 for remote code execution, after probing CVE-2018-13379, CVE-2022-42475, and CVE-2023-27997. The actor also probed F5 BIG-IP for CVE-2021-22986, CVE-2022-1388, and CVE-2023-46747, escalated privileges with PwnKit and Dirty COW, used MeshCentral as a C2 backdoor, harvested SSH/database/SNMP/Radius credentials, deployed PHP web shells, and ran cleanup scripts to hide the intrusion.
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Attackers Actively Exploiting Critical Vulnerability in WooCommerce Wholesale Lead Capture Plugin
Attackers are actively exploiting an unauthenticated arbitrary file upload flaw in the WooCommerce Wholesale Lead Capture plugin, enabling PHP backdoors and remote code execution.
A critical unauthenticated arbitrary file upload vulnerability in WooCommerce Wholesale Lead Capture, a premium WordPress plugin with an estimated 6,000 active installations, was publicly disclosed on February 20, 2026. Wordfence reports attackers are now actively exploiting the flaw to upload arbitrary files, including PHP backdoors, and achieve remote code execution. No CVE ID was cited in the report.
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Palo Alto Networks Patches Authentication Bypass Exploit in PAN
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Hackers Exploit FortiGate SSL-VPN Flaw to Breach Thai ISP and Deploy MeshCentral Backdoor
Threat actors exploited FortiOS SSL-VPN flaw CVE-2024-21762 to breach Thai ISP Triple T Broadband, gaining root-level persistence via MeshCentral agents.
Attackers exploited CVE-2024-21762, an out-of-bounds write enabling unauthenticated RCE in FortiOS SSL-VPN, against Triple T Broadband's FortiGate 60F at mail.3bb.co.th, launching a Node.js reverse shell via a ROP payload. Hunt.io uncovered the operation through an exposed staging directory at 92.63.180[.]133:8888 containing 298 files of exploits, credential-harvesting scripts, session cookies, and a device inventory. Post-compromise, the actors deployed MeshCentral agents (device group TH-3BB, C2 www.ayuthayatech.com) running as root, plus a hidden SUID backdoor at /usr/local/bin/.rc, and also targeted an internal Pentaho/Tomcat server with Ghostcat (CVE-2020-1938). A cleanup script removed logs, shell histories, and web shells while deliberately preserving the MeshCentral agent and SUID backdoor.
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Five Critical WordPress Plugin and Theme Flaws Enable Site Takeover or RCE
Five critical flaws (CVSS 9.8–10.0) in WPMU DEV Dashboard, Avada, TranslatePress, Pods, and GiveWP enable WordPress admin takeover and RCE.
Wordfence and Patchstack disclosed five critical flaws in WordPress plugins and themes: WPMU DEV Dashboard, Avada, TranslatePress, Pods, and GiveWP. The issues include unauthenticated authentication bypass (CVE-2026-76581), arbitrary file write leading to RCE (CVE-2026-18431), administrator account takeover via password-reset URL exposure (CVE-2026-19632), privilege escalation (CVE-2026-19598), and PHP object injection to RCE (CVE-2026-82222, CVSS 10.0). Patchstack says the GiveWP flaw chains an unsafe unserialize helper, attacker-controlled donation data, and a gadget chain in shipped code.
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Threat Brief: Ongoing Russia and Ukraine Cyber Activity
Ukrainian government sites were defaced via OctoberCMS CVE-2021-32648 while Microsoft-attributed actor DEV-0586 deployed destructive WhisperGate malware.
Unit 42 tracks January 2022 attacks against Ukrainian government websites that were defaced or made inaccessible, which Ukraine attributed to Russia. Attackers exploited CVE-2021-32648, an account takeover flaw in OctoberCMS prior to 1.0.472, by submitting a boolean true as the password reset code to bypass validation. Separately, WhisperGate malware, attributed by Microsoft to DEV-0586, disabled Windows Defender and corrupted files across multiple Ukrainian organizations, using a ransomware-appearing first stage and an HTTPS-beaconing second stage with LOLBINs and anti-analysis techniques.
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