CVE-2026-104477 Showdown through 2.1.0 XSS via unescaped quote in href and src attributes
Attackers can execute arbitrary scripts via crafted markdown links or images due to unescaped quotes in href and src attributes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-104477?
CVE-2026-104477 is a medium-severity cross-site scripting vulnerability in showdownjs showdown, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-79
Which versions are affected by CVE-2026-104477?
How do I fix CVE-2026-104477?
No fix has been published for CVE-2026-104477 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-104477 being exploited?
There is no known exploitation of CVE-2026-104477 in the wild and no public exploit code.
Sources
Also known as GHSA-gc85-xrjc-cv75.