GHSA-fg94-h982-f3mm: Claude Code: Out-of-Band Data Exfiltration via Pre-Approved HuggingFace Domain in WebFetch

Claude Code had a security flaw where the domain huggingface.co was automatically approved for the WebFetch tool (a feature that lets AI systems fetch data from the internet), allowing attackers to trick Claude into making web requests to attacker-controlled files and secretly stealing data like files or environment variables without user permission. An attacker would need to first inject malicious content into Claude's context (the information it's working with) to exploit this vulnerability.