Establishing RDP Sessions using mtsc /admin not working on SPS after upgrade (4378449)

After upgrading attempts to connect to the destination using mstsc /admin are now failing where they previously worked. 

The function for 'mstsc /admin' had not previously been tested and officially supported. In some scenarios it was working but that was unexpected. 

A RDP vulnerability was discovered and patched in the product and once that issues was resolved this switch stopped working.

Please see KB 4376565 for additional details. 

WORKAROUND 

The only workaround is to stop using the /admin switch.

RESOLUTION

Defect number 340458 has been raised to investigate the possibility of supporting this behavior securely in a future version.