js-yaml 4.2.0

npm / js-yaml / 4.2.0 source ↗

[4.2.0] - 2026-06-01

Added

• Added docs/safety.md with notes about processing untrusted YAML.
• Added maxDepth (100) loader option. Not a problem, but gives a better exception instead of RangeError on stack overflow.
• Added maxMergeSeqLength (20) loader option. Not a problem after merge fix, but an additional restriction for safety.
• Added sourcemaps to dist/ builds.

Changed

• Stop resolving numbers with underscores as numeric scalars, #627.
• Switched dev toolchains to Vite / neostandard.
• Updated demo.
• Reorganized tests.
• dist/ files are no longer kept in the repository.

Fixed

• Fix parsing of properties on the first implicit block mapping key, #62.
• Fix trailing whitespace handling when folding flow scalar lines, #307.
• Reject top-level block scalars without content indentation, #280.
• Ensure numbers survive round-trip, #737.
• Fix test coverage for issue #221.
• Fix flow scalar trailing whitespace folding, #307.
• Fix digits in YAML named tag handles.

Security

• Fix potential DoS via quadratic complexity in merge - deduplicate repeated elements (makes sense for malformed files > 10K).