PUP.Optional.Wajam is the detection name for Wajam, a browser add-on marketed as a “social search.”
This is a generic detection for values under the registry key, HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run, that point to a file called Chrome.exe. However, the said file is not the actual Chrome browser executable. In most cases, this is a Chromium build that is planted by malware or PUPs.
Malwarebytes can remove these values without further user interaction, but this detection is usually part of a larger infection, so you may find more detections if you scan the affected system.