Severity: Critical
CVSS Score: 9.3
**Overview** The Auth0 Symfony SDK contains a critical vulnerability due to insecure deserialization of cookie data. If exploited, since SDKs process cookie content without prior authentication, a threat actor could send a specially crafted cookie containing malicious serialized data. **Am I Affected?** You are affected by this vulnerability if you meet the following preconditions: 1. Applications using the Auth0 Symfony SDK, versions between 5.0.0 BETA-0 to 5.0.0. 2. Auth0 Symfony SDK uses the Auth0-PHP SDK with version 8.0.0-BETA3 to 8.3.0. **Fix** Upgrade Auth0/symfony to the latest version (v5.4.0). **Acknowledgement** Okta would like to thank Andreas Forsblom for discovering this vulnerability.