Xygeni GitHub Action Compromised via Tag Poisoning in 2026
In early March 2026, Xygeni's GitHub Action, xygeni-action, was compromised through a tag poisoning attack. An attacker with access to compromised credentials created pull requests injecting obfuscated shell code into action.yml. Although these pull requests were blocked by branch protection rules and not merged into the main branch, the attacker exploited the compromised GitHub App credentials to move the mutable v5 tag to point at a malicious commit. This allowed any workflow referencing xygeni/xygeni-action@v5 to fetch and execute the compromised code, resulting in a supply chain compromise via tag poisoning. Workflows using xygeni/xygeni-action@v5 during the affected window (approximately March 3–10, 2026) executed a command-and-control (C2) implant that granted the attacker arbitrary command execution on the CI runner for up to 180 seconds per workflow run. This incident underscores the critical need for robust security measures in CI/CD pipelines to prevent similar supply chain attacks.
Kill Chain
