CVE-2026-104477

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.

CVSS 4.0

5.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

CVSS 3.1

6.1CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

0.2% chance of exploitation in the next 30 days; higher than 8% of CVEs (scores of 2026-10-25)

CWE

CWE-79

Published

2026-10-03

Modified

2026-10-06

Record from

the NVD, synced 2026-10-19

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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