In Valve Steam Client for Windows through 2019-08-07, HKLM\SOFTWARE\Wow6432Node\Valve\Steam has explicit "Full control" for the Users group, which allows local users to gain NT AUTHORITY\SYSTEM access.

** DISPUTED ** In Valve Steam Client for Windows through 2019-08-07, HKLM\SOFTWARE\Wow6432Node\Valve\Steam has explicit "Full control" for the Users group, which allows local users to gain NT AUTHORITY\SYSTEM access. NOTE: the vendor disputes the significance of this finding; the discoverer was reportedly told that the Steam threat model excludes "Attacks that require physical access to the user's device" and "Attacks that require the ability to drop files in arbitrary locations on the user's filesystem" (which might apply to the attacker's ability to create links under HKLM\SOFTWARE\Wow6432Node\Valve\Steam\Apps).