All security products run at the Software Level on Windows and have vulnerabilities wherever they are known or unknown.
They all can be exploited if some hacker puts time and effort into finding ways to bypass them.
That is why UAC still offers better protection since it runs at the Windows kernel level above all software.
So the more software you have installed including security software, then more vulnerable you will make your system to be exploited.
Each installed software opens a gate to be exploited. But the best thing is UAC can block software level exploits. HIPS, sandboxing or even virtualization can be bypassed more easily.
On Windows 8, Windows Defender also runs at Windows Kernel level making it harder to bypass compared to third-party security products.
But MSE just runs at software level like the rest of the security products.
Enjoy!!
