A security researcher found a flaw in Anthropic’s Claude Code GitHub Action that let an attacker take over vulnerable public repositories running it, with nothing more than a single opened GitHub issue. Because Anthropic’s own action repo used the same workflow, a working attack could have pushed malicious code into the action itself and onto the projects downstream that pull it.
RyotaK of GMO Flatt Security reported the core bypass to Anthropic in January, and Anthropic fixed it within four days, with further hardening through the spring; the fixes are in claude-code-action v1.0.94. Anthropic rated the issues 7.8 under CVSS v4.0 and paid a bug bounty.
Claude Code GitHub Actions drops Claude into CI/CD pipelines to triage issues, slap on labels, review pull requests, or run slash commands. By default, the workflow gets read and write access to a repo’s code, issues, pull requests, discussions, and workflow files. Because those permissions are broad, the action is supposed to be picky about who can trigger it: only users with write access.
The trigger check had a hole. It waved through any actor whose name ended in [bot], on the assumption that GitHub Apps are trusted things admins install. Trouble is, anyone can register a GitHub App, install it on a repo they own, and use its token to open an issue or pull request on any public repository. The action saw “a bot” and let the attacker’s content through. Tag mode had an extra check to confirm the actor was a real human; agent mode didn’t, which left it open.
From there, the attacker leans on indirect prompt injection, the trick of planting instructions inside content that an AI reads so the model follows them instead of its actual task. RyotaK wrote an issue whose body looked like an error message, then refined the prompt until Claude would “recover” by running the commands buried in it. The target is /proc/self/environ, the Linux file that holds a process’s environment variables, secrets included. Claude Code blocks naive reads, but RyotaK bypasses the guard anyway and gets Claude to write the values back into the issue, where the attacker can grab them.
The real prize in those variables is the credential pair GitHub Actions uses to request an OIDC token, a signed token that proves “I’m this workflow running in this repo.” Claude Code trades that token with Anthropic’s backend for a Claude GitHub App installation token with write access. Steal those credentials, replay the exchange, and you hold write access to the target’s code, issues, and workflows. Aim it at the claude-code-action repo itself, and you could poison the action that downstream projects pull.
RyotaK also flagged a softer route that skipped the bot trick entirely. Anthropic’s own example issue-triage workflow shipped with allowed_non_write_users: “*”, which lets anyone trigger it, a setting Anthropic’s docs already flag as risky. Worse, Claude was posting…
Source link
Disclaimer
We strive to uphold the highest ethical standards in all of our reporting and coverage. We blogs.grocliq.com want to be transparent with our readers about any potential conflicts of interest that may arise in our work. It’s possible that some of the investors we feature may have connections to other businesses, including competitors or companies we write about. However, we want to assure our readers that this will not have any impact on the integrity or impartiality of our reporting. We are committed to delivering accurate, unbiased news and information to our audience, and we will continue to uphold our ethics and principles in all of our work. Thank you for your trust and support.
Website Upgradation is going on for any glitch kindly connect at [email protected]
