PC: The latest version on PC is 2.6.9. You can find that here named Modern Firearms 2.6.9 – Downloads

Xbox: The latest version on Xbox is [XB1] Modern Firearms V2.5-1.4 (Temporary) 2.6.x has not released for Xbox yet but will release “Soon™”. We have some bugs to squash on PC first before considering an Xbox upload. There is no ETA/date.

Basic rule of thumb: If there are multiple versions of a mod, go with whatever one has the latest/highest version number or has the most recent “Uploaded/Created” date. It most commonly means it is the best/latest version. And NEVER install more than one version. Yes Xbox users, we mean you. More than a few of you have asked if you need to install multiple versions. NO! You don’t.