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markdown-it: Quadratic CPU usage in smartquotes rule (typographer: true)

A quadratic time complexity vulnerability in markdown-it's smartquotes rule (enabled via `typographer: true`) causes excessive CPU usage when processing many co

16 Jun 2026Read 1 minSeverity: schedule it

What changed

A quadratic time complexity vulnerability in markdown-it's smartquotes rule (enabled via `typographer: true`) causes excessive CPU usage when processing many consecutive quotation marks, leading to denial of service.

Who it affects

Applications that render user-supplied markdown with `typographer: true` enabled.

What to do today

Disable the `typographer` option if not needed, or apply a patch that replaces the `replaceAt()` approach with an O(n) method.

The trail
Collected Audited Written Published