Possible Adware? PUP.Optional.Installrex

I was doing a weekly routine Malwarebytes scan yesterday. However, it came across a .part file in my Temp folder that was said to be identified with PUP.Optional.Installrex. Since it is a .part file, I'm assuming it came from Firefox.
I let it quarentine the file, which I deleted after rebooting. I've apparently had this file in my Temp folder for the past 5 days, and the computer has still been acting completely normally. I also ran a scan with AdwCleaner.exe, which came up clean, and the file hasn't come back. Is there anything else I should do?
I want to make sure that this was just a random file and not part of a greater infection.

Here's the Malwarebytes log in question:

Malwarebytes : Free anti-malware download

Database version: v2013.08.25.06

Windows 8 x64 NTFS
Internet Explorer 10.0.9200.16660
Karat_000 :: DRIFLOONEMPIRE [administrator]

8/30/2013 6:56:36 PM
mbam-log-2013-08-30 (18-56-36).txt

Scan type: Quick scan
Scan options enabled: Memory | Startup | Registry | File System | Heuristics/Extra | Heuristics/Shuriken | PUP | PUM
Scan options disabled: P2P
Objects scanned: 236410
Time elapsed: 2 minute(s), 21 second(s)

Memory Processes Detected: 0
(No malicious items detected)

Memory Modules Detected: 0
(No malicious items detected)

Registry Keys Detected: 0
(No malicious items detected)

Registry Values Detected: 0
(No malicious items detected)

Registry Data Items Detected: 0
(No malicious items detected)

Folders Detected: 0
(No malicious items detected)

Files Detected: 1
C:\Users\Karat_000\AppData\Local\Temp\a_AoB44i.exe.part (PUP.Optional.Installrex) -> Quarantined and deleted successfully.

(end)