Vulnerability · Published Jul 23, 2026 · Assigned by VulnCheck

CVE-2026-65697Fathom Lite 1.3.1 Stored XSS via /collect Endpoint

Medium 6.1

In plain English

A medium-severity cross-site scripting in fathom from usefathom. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.3%top 80.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Fathom Lite through 1.3.1 contains a stored cross-site scripting vulnerability in the analytics collection endpoint that allows unauthenticated attackers to inject a javascript: URI into the Top Pages dashboard by supplying a crafted hostname and pathname to the unauthenticated /collect endpoint. The parseHostname and parsePathname functions perform no URI scheme validation, allowing a javascript: hostname combined with a newline-prefixed pathname to be stored and later rendered as an anchor href in the authenticated dashboard without sanitization, enabling session hijacking and full account takeover when an operator clicks the poisoned entry.

Affected products (as reported)

Vendor	Product	Versions
usefathom	fathom	0 – through 1.3.1

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

Researcher Disclosure technical-description, exploit
https://www.vulncheck.com/advisories/fathom-lite-stored-xss-via-collect-endpoint third-party-advisory