Server-Side Request Forgery via Favicon Retrieval in Lookyloo PlaywrightCapture

Summary

A Server-Side Request Forgery (SSRF) vulnerability existed in Lookyloo's PlaywrightCapture when the only_global_lookup option was enabled.

PlaywrightCapture implements this option to prevent captures from accessing local, loopback, or otherwise non-public network resources. However, favicon retrieval was performed separately from the browser request-routing protections. Favicon URLs extracted from rendered HTML were resolved and subsequently fetched directly using an aiohttp.ClientSession.

An attacker able to supply or control a web page processed by PlaywrightCapture could include a crafted favicon reference, for example pointing to a loopback address, private IP address, or another resource reachable only from the PlaywrightCapture host. When the page was processed, the favicon retrieval routine could issue an HTTP request to this destination despite only_global_lookup being enabled.

This bypass could therefore be used to make the PlaywrightCapture host interact with internal network services that should not be reachable through a capture. Depending on the targeted service and its response, this could enable internal service discovery, access to internal resources, or interaction with HTTP endpoints available only from the capture infrastructure.

The patch introduces a common URL validation routine and applies it to favicon retrieval. Direct non-global IP addresses, localhost, .local domains, malformed URLs, and other explicitly non-public destinations are rejected before the favicon request is performed.

This fix is a complementary fix to CVE-2026-44439 - GCVE-0-2026-44439 - GHSA-687H-XW6F-Q2QW