6.1.5

• fix: parse flat selectors in linear time, closing a CPU exhaustion vulnerability (CVE-2026-104844 / GHSA-rj75-hqrm-r3gf, reported by Wayde Shi), backported from 7.1.6 (#346 by @bradyshutt)

The 6.x line is now in security-only maintenance

This release exists because the advisory above covers every published 6.x
version, and until now the only remediation on offer was an upgrade to 7.x.
6.1.5 is the patched version for the 6.x line.

The line is kept alive for the installed base that cannot move to 7 yet, Tailwind
CSS 3 in particular, which depends on ^6.1.2. From here on it receives security
fixes only: no features, no other bug fixes, no type changes. Everything else
goes to 7.x, where this package is actively developed. Tailwind CSS 4 no longer
depends on this package at all, so this line is expected to retire on its own.

6.1.5 is published under the legacy-v6 npm dist-tag, so
npm install postcss-selector-parser keeps resolving to 7.x. Existing ^6
ranges pick up 6.1.5 as usual.