Windows Media Player Firefox Plugin

My son visited a site which is known to have malware from howmanyoffers.com.

 

Despite the warning he proceeded and manged to download "Windows Media Player Firefox Plugin" as he wanted to view a video.

 

I have no idea if it is really malware although it states that the publisher is "Microsoft Corp" but when I go to uninstall the publisher comes up as "an unidentified program wants access to your computer"... "Unidentified Publisher"

 

What to do, can I just proceed with the uninstal?

 

Thanks in advance