The C:\Program Files (x86)\Splashtop\Splashtop Software Updater\uninst.exe process creates a folder at C:\Windows\Tempnsu.tmp and copies itself to it as Au_.exe. The C:\Windows\Tempnsu.tmp\Au_.exe file is automatically launched as SYSTEM when the system reboots or when a standard user runs an MSI repair using Splashtop Streamer’s Windows Installer. Since the C:\Windows\Temp~nsu.tmp folder inherits permissions from C:\Windows\Temp and Au_.exe is susceptible to DLL hijacking, standard users can write a malicious DLL to it and elevate their privileges.

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-3181
• https://github.com/mandiant/Vulnerability-Disclosures/blob/master/2023/MNDT-2023-0015.md