Fix _minimize() race in forward_event stripping WEB_PARAMETER fields - #3163
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forward_event() distributes events to modules via sequential awaits. Between iterations, a fast module can process the event and call _minimize(), dropping _module_consumers to 0 and stripping fields like original_value before slower modules are even queued. Add a sentinel (+1 before the loop, _minimize() after) so the counter never transiently hits 0 during distribution. Also use defensive .get() in lightfuzz metadata() as a belt-and-suspenders guard.
ausmaster
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Jun 11, 2026
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## dev #3163 +/- ##
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+ Coverage 91% 91% +1%
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Summary
forward_event()distributes events to modules via sequentialawait module.queue_event(event)calls. Between iterations, the event loop can schedule a fast module's worker, which processes the event and calls_minimize(). If_module_consumerstransiently hits 0 mid-loop,_minimize()strips fields likeoriginal_value,additional_params, andassigned_cookiesfromWEB_PARAMETERevents before slower modules (like lightfuzz) are even queued. This causedKeyError: 'original_value'crashes in lightfuzz'smetadata()for every COOKIE-typeWEB_PARAMETER.Fix: Add a sentinel hold on
_module_consumers(+1 before the distribution loop,_minimize()after) so the counter never transiently reaches 0 during distribution. Also use defensive.get()in lightfuzzmetadata()as a belt-and-suspenders guard.Regression test:
test_web_parameter_minimize_sentinelmonkey-patches output modules to simulate instant processing, reorders modules so fast ones iterate before the slow one, then calls realforward_event()and assertsoriginal_valuesurvives. Confirmed: fails without fix, passes with fix. All 112 lightfuzz tests pass.