On March 12, 2023, our production API serving 142,000 daily active users was fully exposed to the public internet for 2 hours and 17 minutes due to a misconfiguration in Deno 1.9’s built-in HTTP server and a gap in our security audit pipeline. We lost zero user data, but the near-miss cost us 120 engineering hours in remediation, $14k in emergency on-call pay, and a temporary 18% drop in user trust metrics. The vulnerability stemmed from a known (but unpatched) path traversal flaw in Deno 1.9.0’s standard library HTTP module, combined with our team’s over-reliance on overly permissive --allow-net flags and unvalidated dynamic imports in our edge runtime code. This postmortem breaks down exactly what went wrong, how we fixed it, and the benchmarks we used to validate our remediation efforts.…