GHSA-j95f-988m-3j2f

## Summary `@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. ## Block attribute root cause `packages/core/src/utilities/markdown/attributeUtils.ts` uses both `matchAll` and `replace` with `/([a-zA-Z][\w-]*)\s*=\s*(__QUOTED_\d+__)/g`. The candidate is `'__QUOTED_0'.repeat(n) + '__QUOTED_0__'`. There are no quotes, so the preceding replacement leaves it unchanged. At each `Q`, the greedy key-name expression consumes the remaining word-character run, the required equals sign fails, and the unanchored engine restarts at the next `Q`. This yields `O(n^2)` work, and the cleanup pass repeats it. A complete public-API proof is: ```js import { createAtomBlockMarkdownSpec } from '@tiptap/core' const tokenizer = createAtomBlockMarkdownSpec({ nodeName: 'probe' }).markdownTokenizer const attack = '__QUOTED_0'.repeat(2048) + '__QUOTED_0__' const source = `:::probe {${attack}} :::\n` const started = performance.now() tokenizer.tokenize(source, [], {}) console.log(performance.now() - started) ``` Measured complete-tokenizer timings were 6.23, 23.12, 88.93, 369.10, and 1,400.17 ms at 1,308, 2,588, 5,148, 10,2