On November 2, an attacker used compromised credentials to enter the update system of cPGuard, a security suite for Linux web-hosting servers, and pushed a malicious script in versions 5.88.12 through 5.88.19. The script installed a backdoor and collected password hashes, root SSH keys, the MySQL root password and root’s shell history. The vendor, OPSSHIELD, says about 2,950 customer servers ran it and traced the attack to a break-in at its billing and licensing server. The attacker also copied three of OPSSHIELD’s cloud servers and took billing records for about 7,900 customer accounts. OPSSHIELD detected the attack within 12 hours. Updating removes the backdoor but does not cancel the stolen credentials. The tool meant to protect the server became the way in.
WHAT TO DO
- If you or your hosting provider run cPGuard, update to the latest version and confirm the script’s leftover files are gone.
- Treat any server that installed versions 5.88.12 through 5.88.19 as compromised, even after updating.
- From a trusted environment, reset root and local passwords, rotate database passwords and cloud keys, and replace SSH keys.
- Remove the old public keys from every system that trusted them.
- Ask hosting and managed service providers which security agents run on your servers and how they protect those update channels.
Sources: The Hacker News, Swati Khandelwal, “cPGuard Update Channel Hijacked to Backdoor Linux Servers and Collect Password Hashes,” November 3, 2026; BleepingComputer, Bill Toulas, “Hackers hijack cPGuard autoupdate to deploy backdoor, steal data,” November 3, 2026