Executive brief
Lightpanda is a headless web browser used for AI and automation tasks. A security flaw allowed the browser to incorrectly send sensitive session cookies to websites even when instructed not to, or when making requests to different domains. This could allow a malicious website to perform unauthorized actions on behalf of a user (such as changing account settings or accessing private data) if the browser session had previously logged into other services.
Technical details
A vulnerability exists in Lightpanda's fetch() and XMLHttpRequest implementations where session cookies are unconditionally attached to outgoing HTTP requests. The browser fails to honor the 'credentials' mode (omit, same-origin, include) and the 'XMLHttpRequest.withCredentials' property. This flaw allows an attacker-controlled origin to perform authenticated cross-origin requests (CSRF) against victim origins if the Lightpanda session has active cookies for those origins. The issue stems from a lack of origin validation in the cookie-handling logic within the networking stack. The vulnerability is addressed in version 0.2.9 by ensuring the cookie jar is only included for 'include' or 'same-origin' requests as appropriate.
Affected products
- lightpanda-io Lightpanda Browser < 0.2.9
Timeline
- 2026-04-14: patched: Fix merged via pull request #2155
- 2026-04-24: advisory: Release 0.2.9 published
- 2026-05-28: advisory: GitHub Security Advisory published
- 2026-07-15: disclosed: CVE published to NVD