league/commonmark: DisallowedRawHtml bypassed when a disallowed tag name ends the raw-HTML literal

Summary The DisallowedRawHtml extension does not escape a disallowed tag when the tag name is the last thing in the raw HTML. A Markdown line containing just /i The trailing character class requires one character after the tag name. The block parser does not: RegexHelper::PARTIALHTMLBLOCKOPEN...

PT-2026-68929

Impact Affected versions of league/commonmark can have quadratic time complexity when parsing specially crafted Markdown lines. In practical terms, doubling the length of an affected line can make the parser perform roughly four times as much work. The parser identifies locations using character...