ProxyShell refers to a group of critical security vulnerabilities found in Microsoft Exchange email servers, first disclosed in 2021. These flaws allow attackers to bypass authentication and remotely execute code on affected servers, potentially gaining full control over email systems and sensitive data. Cybercriminals have widely exploited ProxyShell to install malware, steal information, and launch further attacks. The vulnerabilities highlight the importance of keeping software updated and applying security patches promptly to protect against unauthorized access.