🛡️ Sentinel: [HIGH] Fix prototype pollution in Lua labels

[ericbfriday]

🚨 Severity: HIGH
💡 Vulnerability: The parser used an object literal ({}) to store user-defined Lua labels. This exposed the parser to prototype pollution if a malicious script used label names that conflict with Object.prototype properties (like __proto__, toString, etc.), potentially causing unexpected behavior or crashes during parsing.
🎯 Impact: Maliciously crafted Lua code could cause prototype pollution within the parser runtime, potentially leading to denial of service, crashes, or unpredictable state corruption.
🔧 Fix: Changed the initialization of scope.labels from {} to Object.create ? Object.create(null) : {}. This ensures the dictionary map used to store label strings has a null prototype, mitigating prototype pollution vulnerabilities while maintaining backward compatibility with older JavaScript environments.
✅ Verification: Verified that tests pass via npm run test and npm run bench:luast. Verified that luaparse.js uses the new null-prototype initialization. Documented the learning in .jules/sentinel.md.

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PR created automatically by Jules for task 4108014751997199802 started by @ericbfriday

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Pull request overview

This PR hardens luaparse’s control-flow label tracking against prototype pollution by ensuring label dictionaries don’t inherit from Object.prototype, and records the security learning in repository documentation.

Changes:

• Initialize scope.labels with a null-prototype object (Object.create(null)) to prevent prototype pollution from user-controlled label names.
• Add a Sentinel security note documenting the vulnerability and the prevention pattern.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
luaparse.js	Switches the labels map to a null-prototype dictionary to mitigate prototype pollution.
.jules/sentinel.md	Documents the vulnerability, learning, and recommended prevention pattern.

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