What’s Vulnerable › Vulnerabilities

CVE-2026-104477: Showdown through 2.1.0 XSS via unescaped quote in href and src attributes

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-03 · updated 2026-10-06
• Weakness: CWE-79

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.

Affected products

• showdownjs showdown: through 2.1.0

References

• https://github.com/showdownjs/showdown
• https://github.com/showdownjs/showdown/commit/4fb992cd26631c108ec0410342630c80207ec7c6
• https://www.vulncheck.com/advisories/showdown-through-2.1.0-xss-via-unescaped-quote-in-href-and-src-attributes

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