Official MCP Python SDK Flaw Can Let Malicious Servers Steal OAuth Credentials

A security flaw in the official MCP Python SDK allowed malicious servers to steal OAuth credentials by redirecting login data to attacker-controlled endpoints. The vulnerability affects versions before 1.30.0 and 2.2.0, enabling attackers to obtain valid access tokens with app permissions. The issue was reported by Cycode and rated high severity for unattended providers.