GHSA-JJV6-8J6V-6J52 league/commonmark: Denial of service in the SmartPunct and Attributes extensions

Impact Two first-party extensions contain quadratic parsing paths. Both ship with the library but must be explicitly registered on the Environment; neither is included in CommonMarkConverter, GithubFlavoredMarkdownConverter, or GithubFlavoredMarkdownExtension. Applications that do not register...

GHSA-F8FG-PG57-V4J8 league/commonmark XSS: `on*` event-handler filter in `AttributesExtension` bypassed with a U+000C form feed

Summary The AttributesExtension documents a security guarantee: Note: Attributes starting with on e.g. onclick or onerror are capable of executing JavaScript code and are therefore never allowed by default. You must explicitly add them to the allow list if you want to use them. —...

CVE-2026-71478

league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension's href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a...

Incomplete Denylist to Cross-Site Scripting

Overview league/commonmark is a PHP-based Markdown parser which supports the full CommonMark spec. It is based on the CommonMark JS reference implementation. Affected versions of this package are vulnerable to Incomplete Denylist to Cross-Site Scripting via the filterAttributes process. An attack...

CVE-2026-71478

league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension's href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a...