CVE-2026-73646 PostCSS: Path Traversal in Previous Source Map Auto-Loading (sourceMappingURL) leads to Arbitrary .map File Disclosure

PostCSS takes a CSS file and provides an API to analyze and modify its rules by transforming the rules into an Abstract Syntax Tree. Prior to 8.5.18, lib/previous-map.js loadMap passes attacker-controlled sourceMappingURL values to joindirnameopts.from, annotation, and loadFile permits traversed ...