I got into YC by hacking it

A founder discovered a security vulnerability in Y Combinator's Paxel application—a tool used to score applicants—that allowed him to forge scores and manipulate the ranking database through an unvalidated HMAC. After publicly disclosing the vulnerability, Y Combinator's Jared Friedman quickly patched the issue and invited the founder to attend Startup School, acknowledging the responsible disclosure despite an earlier private report going unanswered.