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CVE-2026-44896 — Mistune: XSS via unescaped figclass/figwidth in Figure directive

2026-09-29T14:42:30.405850+00:00

Affected: lepture mistune

Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and earlier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer. Version 3.2.1 contains a patch.

GHSA-58cw-g322-p94v — Mistune has XSS via unescaped figclass/figwidth in Figure directive

2026-09-29T14:42:30.405985+00:00

Affected: PyPI: mistune

In `src/mistune/directives/image.py`, the `render_figure()` function concatenates `figclass` and `figwidth` options directly into HTML attributes without escaping (lines 152-168).

This allows attribute injection and XSS even when `HTMLRenderer(escape=True)` is used, because these values bypass the inline renderer.

Other attributes in the same file (src, alt, style) are properly escaped; figclass/figwidth were missed.

PYSEC-2026-168

2026-09-29T14:42:30.406040+00:00

Affected: PyPI: mistune

Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and realier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.