CVE-2020-13292: 
GitLab vulnerability analysis and mitigation

In GitLab versions before 13.0.12, 13.1.6, and 13.2.3, a security vulnerability was discovered that allowed attackers to bypass email verification requirements in the OAuth Flow. The vulnerability was assigned CVE-2020-13292 and was disclosed on August 5, 2020 (GitLab Release).

The vulnerability allowed attackers to bypass the email verification check that was required for the OAuth authorization code flow. This bypass could potentially affect third-party applications that use GitLab as an identity provider. The vulnerability received a CVSS v3.1 base score of 9.6 (Critical) with the vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N, indicating a network-accessible vulnerability with low attack complexity (NVD).

The vulnerability could lead to account takeovers on third-party services that use GitLab as an OAuth provider. Attackers could potentially gain unauthorized access to internal company resources that rely on email domain verification for access control. This was particularly impactful because third-party services often use email as an identifier and combine OAuth/manually created accounts (GitLab Issue).

The vulnerability could be exploited by creating a GitLab account with an unverified email address and manipulating the OAuth authorization process. By directly sending a POST request to the /oauth/authorize endpoint with specific parameters, an attacker could bypass the email verification requirement and gain unauthorized access to third-party services (GitLab Issue).

GitLab addressed this vulnerability in versions 13.0.12, 13.1.6, and 13.2.3. Users were strongly recommended to upgrade their GitLab installations to one of these patched versions immediately. The fix implemented proper email verification checks during the OAuth authorization process (GitLab Release).