race-condition

A TOCTOU vulnerability occurs when a system checks a condition and uses the result without atomic controls, allowing concurrent requests to bypass validation. You can detect these time-of-check-to-time-of-use flaws by analyzing concurrent operation failures in workflows like account recovery and inventory management.

The best way to write a proof-of-concept for concurrency bugs is using Go or Python concurrency templates. These templates send parallel requests to target APIs, validating whether backend operations lack proper atomic controls and incorrectly repeat limited-use actions like coupon redemptions.

Yes, you can use concurrency testing for authorized bug bounty assessments. It provides structured strategies to safely test whether financial operations, limited-use resources, and state transitions can be incorrectly repeated through parallel requests without disrupting the target environment.

Your payment API allows duplicate withdrawals under concurrent requests because backend operations lack proper atomic controls. Analyzing these race conditions reveals that state transitions and financial operations are not locked during execution, causing business logic failures.

Yes, this concurrency testing approach works for registration and account recovery flows. It analyzes concurrent operation failures and applies safe validation procedures to detect time-of-check-to-time-of-use vulnerabilities across various state transitions and user workflows.