markdown-it is a Markdown parser. Prior to 14.3.2 and 15.0.2, smartquotes is affected: many opening quotes of one type followed by unmatched closing quotes of the other type cause the smartquotes rule to repeatedly scan the entire opener stack, resulting in quadratic processing time. The root cause is each mismatched quote closer repeatedly scans the opener stack for a compatible quote type. The attack mechanism is quadratic rescanning of the quote opener stack. The affected identifiers are smartquotes and typographer. The trigger conditions are attacker-controlled Markdown with many openers of one quote type and unmatched closers of the other type and typographer mode is enabled. The impact is denial of service through excessive parsing time. The vulnerable path requires typographer mode; disabling typographer or the smartquotes rule prevents the affected processing. This issue is fixed in versions 14.3.2 and 15.0.2.