Stored Cross-Site Scripting in Fathom Lite Analytics by Fathom
CVE-2026-65697

5.1MEDIUM

Key Information:

Vendor

Usefathom

Status
Fathom
Vendor
CVE Published:
23 July 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2026-65697?

Fathom Lite versions up to 1.3.1 are vulnerable to a stored cross-site scripting (XSS) issue that affects the analytics collection functionality. This vulnerability allows unauthenticated attackers to inject malicious JavaScript code via crafted hostname and pathname inputs directed to the /collect endpoint. The inadequate validation in the parseHostname and parsePathname functions enables the injection of a javascript: URI scheme combined with a newline-prefixed pathname to be saved and subsequently rendered within the authenticated Top Pages dashboard. As a result, when a user interacts with the compromised entry, it can lead to session hijacking and comprehensive account takeover.

Affected Version(s)

fathom 0 <= 1.3.1

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2026-65697 - Proof of Concept

References

https://github.com/geo-chen/oss/blob/main/fathom.md
technical-descriptionexploit
https://www.vulncheck.com/advisories/fathom-lite-stored-x...
third-party-advisory

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

George Chen
.