API Authentication Bypass

LLM API authentication typically relies on bearer tokens (API keys), OAuth flows, or JWT-based session tokens. The design assumption is that the authentication layer is distinct from and independent of the model layer. The gap: LLM API authentication systems inherit all traditional web API authentication vulnerabilities, but with higher impact because LLM APIs provide direct access to expensive compute resources and potentially sensitive data.

• Monitor for authentication probing patterns (systematic key format testing)
• Scan for publicly exposed LLM API endpoints (continuous external scanning)
• Alert on API key usage from unexpected IP ranges or geographies
• Track per-key endpoint access patterns — alert on out-of-scope endpoint use

Authentication bypass provides the initial access that enables every other T5 technique. Zero-auth discovery (T5-AP-015G) is the most common entry point in the wild, enabling immediate exploitation of T5-AT-001 through T5-AT-016.