Researcher RyotaK has disclosed a now-patched flaw in Anthropic's Claude Code GitHub Action, which drops Claude into CI/CD to triage issues and review PRs with broad repo permissions. The action's trigger check waved through any actor whose name ended in [bot] - but anyone can register a GitHub App and use its token to open an issue on a public repo. Agent mode lacked the human-actor check tag mode had. The attacker then used indirect prompt injection in an issue to make Claude read /proc/self/environ and write back the OIDC credentials, which can be replayed for an installation token with write access. Anthropic's example workflow shipped with allowed_non_write_users: '*'.
Anthropic appears to be preparing the public rollout of Claude Mythos - the restricted security-focused frontier model that uncovered 10,000 high or critical vulnerabilities in its first month under Project Glasswing. References to 'claude-mythos-1-preview' have briefly appeared in the public Claude Code and Claude Security products, with at least one user reportedly seeing a toggle to enable Mythos before it was pulled. Anthropic originally announced Mythos in early preview on April 7 and held back the public release pending guardrails, warning the model 'can automatically develop functional cyberattacks at a highly professional level.' Pricing and tier availability are not yet disclosed.
TeamPCP's self-propagating supply-chain worm is back in its third iteration, branded 'Shai-Hulud: The Third Coming' in hard-coded strings across the malware. On April 22, Socket reported Checkmarx's official KICS Docker images and a KICS VS Code / Open VSX extension had been trojanized. Bitwarden's own clients repo runs a Checkmarx scan on every pull request via a pull_request_target workflow that holds id-token: write and fetches credentials from Azure Key Vault, so when the poisoned scanner executed it harvested GitHub OIDC and Azure tokens. At 17:57 ET the same day, attackers used those tokens to push a modified publish-cli.yml to the Bitwarden repo and publish a malicious @bitwarden/cli version 2026.4.0 to npm. The package remained live for 93 minutes until Bitwarden pulled it at 19:30 ET. The payload: a 10MB obfuscated credential harvester that grabs SSH keys, cloud provider credentials, npm publish tokens, GitHub tokens, and - new in this variant - MCP (Model Context Protocol) configuration files used by Claude Code, Cursor, and similar AI coding tools. It then self-propagates by republishing into every npm package the victim can modify and uploads encrypted stolen secrets to public GitHub repositories under Dune-themed names. The worm has a Russian-locale kill switch (exits if LC_ALL/LANG starts with 'ru').
Backfill from April 15: OX Security disclosed an architectural flaw in the official Model Context Protocol SDKs (Python, TypeScript, Java, Rust) that lets attacker-controlled JSON config trigger arbitrary OS commands via the STDIO transport. Roughly 200,000 publicly reachable MCP servers and 150 million SDK downloads inherit the issue. OX has tied 14 CVEs to the same root cause across LiteLLM (patched), Bisheng (patched), Windsurf (zero-click RCE in Cursor-style IDEs, still reported), Flowise, LangFlow, GPT Researcher, Agent Zero, and DocsGPT. Anthropic declined to patch the protocol, calling the behavior 'expected.'
TrustStrike Labs