jsfunfuzz and DOMFuzz

Business Profile

Core Value Proposition

jsfunfuzz and DOMFuzz provides testing tools for JavaScript engines and DOM/layout APIs by generating candidate test cases, reducing them to small reproductions, and helping Firefox developers identify and fix bugs, including security vulnerabilities.

Target Customer

{"Mozilla Firefox developers","JavaScript engine teams","Security researchers","Fuzzing and browser testing communities"}

Key Differentiator

Produces reliable, reduced testcases and supports differential testing within the JavaScript engine and DOM/layout testing workflow; emphasizes creating small, reproducible test cases that accelerate bug diagnosis and patching.

Implementation Timeline

Released jsfunfuzz and DOMFuzz on July 28, 2015; described as evolving over approximately 11 years of fuzzing activity with ongoing improvements and community uptake

Pain Points

1Difficulty reproducing bugs from randomly generated inputs
2Need for small, reliable reproduction test cases to speed debugging
3Complex interactions between JS engine components and DOM/layout APIs that are hard to isolate

Key Features

1jsfunfuzz tests JavaScript engines
2DOMFuzz tests layout and DOM APIs
3Testcase reduction to small, actionable reproductions
4Differential testing capabilities (oracle-based consistency checks)
5Controls for fuzzing behavior (e.g., debugging/test controls, GC/JS engine behavior adjustments via testing functions)
6Support for generating test cases that reveal complex interactions and regressions

Target Customer Industries

Client Results

1Discovered 6450 Firefox bugs
2790 of those bugs were security-critical

Competitive Advantages

1Small, reliable testcases enable rapid bug reproduction and isolation
2Improved collaboration with Firefox developers through targeted bug reports
3Support for differential testing reduces false positives and helps verify fixes
4Fuzzers adapted to the Firefox codebase with testing hooks and determinism controls

Key Benefits

1Early detection of bugs and security vulnerabilities

2Small, reproducible reproductions speed debugging and patching

3Facilitates collaboration with developers and patch validation

4Supports differential testing for reliability

Case Studies & Success Stories

Bug 893333 discovered by designMode module interacting with a Firefox developer's table module

Case #1

Bug found through fuzzing interactions between modules; demonstrated the ability to uncover cross-module issues; contributed patch alongside Firefox developers

Bug 1158427 discovered by Christoph Diehl's WebAudio module combined with reflection-based API-discovery modules

Case #2

Illustrates complex module interaction detection via fuzzing; contributed fixes and demonstrated collaborative debugging across modules

Additional Product Information

Product Description

Two fuzzers: one for testing JavaScript engines (jsfunfuzz) and one for testing layout and DOM APIs (DOMFuzz). They generate test cases, reduce them, and help reproduce and report bugs to Firefox developers.

Target Market

Browser/JavaScript engine teams, security researchers, and fuzzing communities focused on browser reliability and security

Unique Value Proposition

Delivers small, reproducible test cases for complex browser bugs and security vulnerabilities, fostering efficient debugging and collaboration with developers through long-term fuzzing engagement

Technical Requirements

Requires a JavaScript engine/Firefox testing environment; supports options such as --fuzzing-safe; uses differential testing and test harness controls; emphasizes reduced testcases and reproducibility

Pricing Model

N/A

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