Thread: Win32.SendMessage() doesn't work for non admin user

If you look at the documentation for SendMessage() on MSDN you will find this little one-liner.

Message sending is subject to UIPI. The thread of a process can send messages only to message queues of threads in processes of lesser or equal integrity level.

The gist is that UIPI (User Interface Privilege Isolation) prevents a program sending messages to a process unless it has sufficient privileges (a process of "higher integrity level" means it is more trusted by the system, hence potentially has more privileges). For example, a normal user will not be able to send messages to windows of programs owned by system accounts (unless specifically granted privileges to do so).

UIPI was introduced in (IIRC) Windows Vista to counter certain techniques of achieving privilege escalation. A number of patches to earlier versions of windows also countered such techniques.

As such, it would be a breach of site policy to discuss techniques to bypass it (other than getting an administrator to grant sufficient privileges). Look at this link (point 6 in particular).

EDIT: and this is a windows question, nothing to do with C++.

Moved to Windows programming forum.