Trojan.Agent refers to a generic Trojan malware detection. It is used for detections that are either associated with no specific malware families or not enough information is available to pinpoint the malware family.
This detection is for a Chrome extension called “Cookies On-Off” that was forced upon visitors of certain compromised sites. The extension is protected against removal by a Chrome policy.
Malwarebytes can remove the extension folder and reset the policy protecting it. The user can then remove the extension manually from the list of installed Chrome extensions.