CVE-2025-66458: Lookyloo has multiple XSS due to unsafe use of f-strings in Markup

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-12-02 · updated 2026-09-25
Weakness: CWE-79

Description

Lookyloo is a web interface that allows users to capture a website page and then display a tree of domains that call each other. Prior to 1.35.3, there are multiple XSS due to unsafe use of f-strings in Markup. The issue requires a malicious 3rd party server responding with a JSON document containing JS code in a script element. This vulnerability is fixed in 1.35.3.

Affected products

lookyloo: before 1.35.3 — fixed in 1.35.3

How to fix

Upgrade to a fixed version: lookyloo 1.35.3. Check the vendor advisory for mitigations.

References

https://github.com/Lookyloo/lookyloo/commit/b6ee2fee0afff0b35f37dd891bbce9d53ed8a290
https://github.com/Lookyloo/lookyloo/security/advisories/GHSA-58h2-652v-gq87

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