Using AI to find authorization bugs — and to prove the ones that aren't real

Using AI to find authorization bugs — and to prove the ones that aren't real Draft flagship post. Safe to publish now (no undisclosed vulnerabilities). The production case study referenced at the end is withheld pending coordinated disclosure. In 2026, bug bounty programs started closing their doors. Nextcloud suspended paid rewards, citing a flood of AI-generated, low-quality reports. Mattermost ended its program. The Internet Bug Bounty cut payouts by roughly 80%. The common thread isn't that AI can't find bugs — it's that most AI-assisted "findings" are plausible but wrong , and triage teams are drowning in them. That reframes the problem. The scarce skill in 2026 isn't generating candidate vulnerabilities — a language model will hand you fifty before lunch. It's refuting the forty-nine that don't hold . The differentiator is a method whose primary output is correct negatives . Here's the method I use for source-available targets, and a worked example where the honest result was "there's no bug here." The method: fan out to find, converge to refute Two stages, two different cost tiers: Fan-out (cheap models). Split the target's authorization surface into subsystems and read each in parallel. Each reader's only job is to surface candidate broken invariants — places where an object is loaded by ID without an owner check, where a protected action might skip a re-auth gate, where two code paths authorize the same thing differently. Optimize for recall. Expect mostly false positives. Adversarial verification (an expensive, high-reasoning model). Take each candidate and try to kill it. Default to REFUTED. A candidate survives only if you can cite the specific source lines proving the guard is absent and the dangerous path is reachable and nothing upstream already blocks it. Frame every survivor as a broken invariant — a one-sentence statement of the rule the system must never violate — and classify it as core versus config-dependent. The output that matters most is the