PUP.Optional.Wajam is the detection name for Wajam, a browser add-on marketed as a “social search.”
This is the general detection for signs on a system that a PowerShell script will be run without user consent.
Malwarebytes can remove this potentially unwanted program (PUP) without further user interaction. If you are aware of the source of the detection and you want to keep it, you can tell Malwarebytes to ignore it in the future by adding it to the exclusions. Read here how to do that.