On May 18, 2026, a massive automated supply-chain attack codenamed Megalodon struck GitHub, injecting malicious CI/CD backdoors into more than 5,500 repositories in under six hours. Security firm SafeDep discovered the campaign, which pushed 5,718 malicious commits to 5,561 distinct repositories using throwaway accounts with randomized eight-character usernames, marking one of the most aggressive GitHub Actions poisoning campaigns ever recorded.
The attackers forged bot-like author identities—build-bot, auto-ci, ci-bot, and pipeline-bot—using emails build-system@noreply.dev and ci-bot@automated.dev to mimic routine automated CI maintenance. Between approximately 11:36 and 17:48 UTC on May 18, these fake commits slipped into repositories without triggering immediate suspicion, as they appeared to be ordinary build optimization updates.
Megalodon deployed two distinct GitHub Actions workflow variants sharing the same command-and-control server at 216.126.225.129:8443. The SysDiag variant added a new ci.yml file triggering on every push and pull_request_target, ensuring automated execution on any commit across all branches. The Optimize-Build variant replaced existing workflows with a workflow_dispatch trigger, creating a dormant backdoor that attackers can silently activate on demand via the GitHub API, producing zero visible CI runs and no failed builds.
The base64-encoded 111-line bash payload conducted aggressive credential harvesting, exfiltrating all CI environment variables, AWS credentials, GCP access tokens, Azure credentials, SSH private keys, Docker and Kubernetes configurations, API keys, database connection strings, GitHub Actions tokens, GitLab CI/CD tokens, and dozens of other secrets while scanning source code for more than 30 secret regex patterns.
The attack’s most critical downstream impact targeted Tiledesk, an open-source live chat platform, where the attacker compromised the repository and replaced the legitimate Docker build workflow. The unsuspecting maintainer published @tiledesk/tiledesk-server versions 2.18.6 through 2.18.12 to npm, propagating the backdoor to the package registry. Organizations should immediately revert malicious commits from build-system@noreply.dev or ci-bot@automated.dev, rotate all secrets, audit cloud logs for anomalous OIDC requests, check Actions tabs for unexpected workflow_dispatch executions, and pin GitHub Actions to specific commit SHAs.
This article has been indexed from CySecurity News – Latest Information Security and Hacking Incidents
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