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.
An exploit kit is a toolkit designed to facilitate the exploitation of client-side vulnerabilities most commonly found in browsers and their plugins in order to deliver malware on end users’ machines.
Malwarebytes can remove this threat without further user interaction. Always consider if this infection is present that exploit drops are usually Trojan droppers that download and run other malware. So there could be more wrong with the affected system.