CamoLeak (CVE-2025-59145, CVSS 9.6) was a high-severity flaw in GitHub Copilot Chat that allowed silent exfiltration of source code, API keys and cloud secrets from private repositories using zero malicious code execution. The attack chain weaponized Copilot's PR-review feature by hiding prompt-injection instructions inside GitHub's invisible markdown comment syntax, which stayed invisible to human reviewers while Copilot ingested them as legitimate commands when a developer asked it to review the pull request. The injected prompt directed Copilot to search the codebase for sensitive data such as AWS keys, encode the findings in base16, and embed each encoded character into pre-signed addresses for GitHub's own Camo image proxy, each pointing to a 1x1 pixel on the attacker's server; because traffic flowed through GitHub's trusted infrastructure, it bypassed the platform's Content Security Policy and standard egress controls. According to BlackFog's writeup, GitHub patched the issue in August 2025 by disabling image rendering in Copilot Chat, and the vulnerability was publicly disclosed in October 2025. Researchers warned that any AI assistant with deep system access, including Microsoft 365 Copilot and Google Gemini, faces the same class of covert exfiltration risk whenever untrusted content can influence its instruction stream.

Sources

• -https://www.blackfog.com/camoleak-how-github-copilot-became-an-exfiltration-channel/
• -https://cybersecuritynews.com/hackers-exploit-github-copilot-flaw/