GitLab RCE Vulnerability: Critical Flaws Expose Default Installations

Executive Summary: A critical remote code execution vulnerability was disclosed in GitLab's notebook diff processing due to two flaws in the Oj Ruby JSON parser; specially crafted .ipynb diffs can trigger arbitrary command execution on affected self-managed GitLab instances (Oj 3.13.0–3.17.1 and multiple GitLab release ranges). GitLab.com was patched, but self-managed administrators are urged to upgrade to the fixed GitLab and Oj versions immediately, audit notebook commits and permissions, and monitor for the provided IoCs.