Description
Basecamp's Google Sign-In adds Google sign-in to Rails applications. Prior to version 1.3.1, it is possible to redirect a user to another origin if the "proceed_to" value in the session store is set to a protocol-relative URL. Normally the value of this URL is only written and read by the library or the calling application. However, it may be possible to set this session value from a malicious site with a form submission. Any Rails applications using the google_sign_in gem may be vulnerable, if this vector can be chained with another attack that is able to modify the OAuth2 request parameters. This issue has been patched in version 1.3.1. There are no workarounds.
References4
Metrics
- CVSS 3.1
-
4.2
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 15 · as of 8 November 2026
- CWE
- CWE-601
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.