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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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StyleSmuggler: Magento and Adobe Commerce 0-day RCE (CVE-2026-75650) under active attack
Sansec details actively exploited StyleSmuggler 0-day (CVE-2026-75650, CVSS 10.0) unauthenticated RCE in Magento and Adobe Commerce, patched by Adobe hotfix APSB26-146.
Sansec is investigating StyleSmuggler, an actively exploited unauthenticated remote code execution chain in Magento Open Source and Adobe Commerce, now tracked as CVE-2026-75650 with CVSS 10.0. Adobe released hotfix VULN-39341 via APSB26-146 (priority 1) on September 7 for versions 2.4.4 through 2.4.9, but stores were being exploited for roughly three days before the fix existed. The implant is a Rust backdoor that disguises itself as kworker, fc-cache, or chronyd processes and exfiltrates host data in MessagePack records sent as fake NTP replies over UDP port 123. Adobe advises rotating the encryption key and every credential it protected, and Sansec stresses patching does not clean already-compromised stores.
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3 Critical Zero-Day Flaws Found in PHP 7 — One Remains Unpatched!
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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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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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Adobe Patches Magento Zero-Day Exploited to Deploy Rust Backdoor and PHP Web Shell
Adobe patches actively exploited Magento zero-day CVE-2026-75650 (CVSS 10.0), abused since Sept 4 to deploy a Rust backdoor and PHP web shells.
Adobe released an emergency hotfix (VULN-39341) for CVE-2026-75650 (CVSS 10.0), dubbed StyleSmuggler by Sansec, which abuses Magento's template system via PHP code injection to trigger unauthenticated remote code execution in Adobe Commerce and Magento Open Source. Exploitation began September 4, 2026, with attackers deploying a Rust-based Linux backdoor and a PHP dropper that writes a web shell; one managed server was compromised 50 minutes after the first report. Previdian honeypots recorded 12 exploitation attempts from two unique IPs in China and Romania since September 7, all unsuccessful. Adobe urges merchants to apply the patch and rotate encryption keys.
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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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