CVE-2026-115910: Python Social Auth: OpenID Connect nonce is not bound to the browser session, so a stolen authorization code logs the attacker in as the victim

Python Social Auth is a social authentication and registration mechanism. Prior to 6.2.0, OpenIdConnectAuth in socialcore/backends/openidconnect.py uses getandstorenonce to place the OpenID Connect nonce in a shared OpenIdConnectAssociation table, and getnonce and validateclaims verify only that the nonce exists and has not expired rather than binding it to the browser session and OAuth state that initiated the login. An attacker who obtains a victim's unused authorization code can start a separate login to obtain valid state for the attacker's browser, submit the victim's code with that state, and pass nonce validation because the victim nonce is globally available. With DEFAULTUSEPKCE disabled in the default OpenIdConnectAuth configuration, the attacker can be logged in as the victim. This issue is fixed in version 6.2.0.