Defender 365 detecting malware in a CAB/DVSSP file

Follow the advise from Tonaco.

Not having the proper exclusions will do more harm than good. As for a possible threat in the cab/dvs files, keep in mind that if a user retrieves the item, it will be scanned on the location where it is opened. Provided ofcourse, the user is running an AV solution also. When a retrieved item is opened on a workstation, then the local AV should kick in, and then clean/quarantine or block the item.