CVE-2026-104477

Showdown through 2.1.0 XSS via unescaped quote in href and src attributes

State: Published
Severity: 5.3 Medium
Published: Oct 2, 2026
Updated: Oct 5, 2026
Reserved: Oct 2, 2026

Description

Showdown through 2.1.0 contains a cross-site scripting vulnerability in the makehtml link and image subparsers, which fail to escape double quotes in destination URLs placed into href and src attributes. Attackers can craft markdown links or images containing a double quote followed by onerror or onmouseover handlers to execute script when victims view rendered HTML.

Scores

CVSS	Score	Vector	Source
4.0	5.3 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N	VulnCheck
3.1	6.1 Medium	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N	VulnCheck

Weaknesses

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Products

Product	Versions
showdownshowdownjs	2.1.0 and earlierAffected

References

Patch Commitpatch
https://github.com/showdownjs/showdownproduct
VulnCheck Advisory: Showdown through 2.1.0 XSS via unescaped quote in href and src attributesthird-party-advisory

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