CVE-2026-104477 PUBLISHED

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

Assigner: VulnCheck
Reserved: 02.10.2026 Published: 02.10.2026 Updated: 02.10.2026

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 Vector: 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
CVSS Score: 5.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	Low
Attack Complexity	Low	Integrity	Low	Integrity	Low
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	None
User Interaction	Passive

CVSS 4.0

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

Attack Vector	Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	None	Integrity Impact	Low
User Interaction	Required	Availability Impact	None

CVSS 3.1

Product Status

Vendor	showdownjs
Product	showdown
Versions	Default: unaffected affected from 0 to 2.1.0 (incl.)

Credits

Muhammad Sobirov finder

References

Problem Types

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