GHSA-j95f-988m-3j2f: Tiptap: Quadratic ReDoS in block and inline Markdown attribute parsing

@tiptap/core contains two quadratic regular-expression denial-of-service paths in its default Markdown attribute parsers. Pandoc-style block attributes use two unanchored greedy expressions that rescan repeated __QUOTED_0 prefixes. Inline shortcode attributes use another unanchored greedy key expression that rescans a long word-character run when no equals sign follows.

The public createAtomBlockMarkdownSpec and createBlockMarkdownSpec helpers call the vulnerable Pandoc-style parser; createInlineMarkdownSpec calls the separately vulnerable shortcode parser. Using unmodified npm 3.29.2, a complete 20,508-byte atom-block token took approximately 1.40 seconds while an equal-length control took 0.29 ms. A complete 32,776-byte inline token took approximately 2.21 seconds while its equal-length control took 0.19 ms. Current repository main commit 5158212970344952dd9918b6a44bfb400d7fb6c1 retains both expressions.