vulnerability / NVI-00018389 / Revision 1
Mistune Math Plugin has an XSS Escape Bypass
GitHub lists this reviewed advisory for mistune. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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6.1 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
mistune
source listed<= 3.2.0
## Summary The mistune math plugin renders inline math (`$...$`) and block math (`$$...$$`) by concatenating the raw user-supplied content directly into the HTML output **without any HTML escaping**. This occurs even when the parser is explicitly created with `escape=True`, which is supposed to guarantee that all user-controlled text is sanitised before reaching the DOM. The result is a silent contract violation: a developer who enables `escape=True` reasonably expects complete XSS protection, but the math plugin operates as an independent render path that ignores the renderer's `_escape` flag entirely. ## Details **File:** `src/mistune/plugins/math.py` ```python def render_inline_math(renderer, text): # `text` is raw user input — no escape() call anywhere return r'\(' + text + r"\)" def render_block_math(renderer, text): # same issue for block-level $$...$$ return '$$\n' + text + "\n$$\n" ``` Both functions take `text` directly from the parsed token and concatenate it into the output string. Neither function: - calls `escape(text)` from `mistune.util` - checks `renderer._escape` - calls `safe_entity(text)` or a
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-8g87-j6q8-g93x ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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