Lightpanda is a headless browser designed for artificial‑intelligence and automation workloads. Prior to version 0.3.1, its URL parser searched for the '@' character across the entire URL string instead of just the authority component when determining a page’s origin. Consequently, a URL such as http://attacker.com/@victim.com/ would be fetched from attacker.com but be treated as belonging to http://victim.com, enabling a complete Same‑Origin Policy bypass. The vulnerability is fixed in release 0.3.1.

The flaw affects the Lightpanda Browser version 0.3.0 and earlier. Upgrade to version 0.3.1 or later resolves the issue; earlier releases remain vulnerable.

With a CVSS score of 9.3 the vulnerability is considered Critical. The EPSS score of less than 1% indicates that the likelihood of observed exploitation is low at present, and the vulnerability is not listed in the CISA KEV catalog. However, the attack vector is a malicious URL that a user can be tricked into visiting or that the browser may load through automated scripts, enabling attackers to read or alter data that should be protected by same‑origin isolation. The weakness is identified as CWE‑346 (Information Exposure Through Misused Redirect).