A time-of-check time-of-use vulnerability in PulseSecureService.exe in Pulse Secure Client versions prior to 9.1.6 down to 5.3 R70 for Windows (which runs as NT AUTHORITY/SYSTEM) allows unprivileged users to run a Microsoft Installer executable with elevated privileges.
https://twitter.com/sepcali/status/1262551597990711296
https://twitter.com/gsepcali/status/1272927080909623297
https://twitter.com/gsepcali/status/1262551597990711296
https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44503
https://kb.pulsesecure.net/?atype=sa
http://seclists.org/fulldisclosure/2020/Sep/15
http://seclists.org/fulldisclosure/2020/Jun/25
http://packetstormsecurity.com/files/159065/Pulse-Secure-Windows-Client-Privilege-Escalation.html