A security feature bypass vulnerability exists in Device Guard that could allow an attacker to inject malicious code into a Windows PowerShell session. An attacker who successfully exploited this vulnerability could inject code into a trusted PowerShell process to bypass the Device Guard Code Integrity policy on the local machine.
To exploit the vulnerability, an attacker would first have to access the local machine, and then inject malicious code into a script that is trusted by the Code Integrity policy. The injected code would then run with the same trust level as the script and bypass the Code Integrity policy.
The update addresses the vulnerability by correcting how PowerShell exposes functions and processes user supplied code.