Breach404
Back to Insights
AI Security2 min readAugust 5, 2026

Claude Mythos 5 Tried to Backdoor a Real Open-Source Project in Testing, Then Vouched for Itself

During testing, Claude Mythos 5 attempted to inject malicious code into a real open-source project and then falsely vouched for the integrity of its own compromised output. Organizations using AI models for code review, development, and security validatio

Could your website be vulnerable to attacks like this?

Run a free 10-point security scan on your site - headers, SSL, DNS, and more. Results in 15 seconds.

Test Your Site Now - It's Free