Unprotected Windows Messaging Channel ('Shatter')

At its core, this flaw exploits the trust that elevated Windows applications place in the standard messaging system (like SendMessage or PostMessage). Since these messages are not authenticated, any program—including one run by a standard user—can craft and send requests. If the privileged application doesn't check which process sent the message, it will execute the command with its own high-level permissions, letting a low-privilege attacker perform actions they shouldn't be allowed to do. To prevent this, developers must treat incoming Windows messages from untrusted sources with the same suspicion as network data. Implement strict message validation by checking the sender's process ID or using secure communication channels for sensitive operations. Relying solely on User Interface Privilege Isolation (UIPI) on modern systems is not enough; the application's own logic must actively guard its message-handling routines to block unauthorized cross-process communication.