It's pretty typical for shitty borderline-adware AV programs like McAfee and Norton to throw up constant false positives and outright fake "viruses" on their scans to try to convince you that you're in danger and they're stopping it (often while they ignore actual threats).
I've got one machine here that hasn't been connected to anything (live[1]) for
years. The free-version AV installed on it and that I haven't bothered uninstalling (identified as the 2012 version) occasionally[2] pops up a message saying I have been "protected from theats", and gives the actual count. Which it actually lists as zero. Must make note of the number of scans it tells me that was from, next time it pops up.
Another free-AV I've used (on less isolated machines, but not important enough to be up-protected to the next level) does an annual "renew your free licence" thing that is
always trying to misguide the user to 'temporarily' use the Premium Trial, which it's all too easy to do by clicking on the 'obvious' hotspots. And then if I (or the people using it at the time) don't notice and manually revert, a month or so later there's demand for payment. I rather dislike Trial Premium systems, because of tricks like this. Full Paid, or let me (or the other poor victim) keep with the Free Version I selected, please.
And because I've always had a different monitoring AV already, MBAM has only ever been useful to me as an on-demand scanner, every now and then, for which the Premium is truly a waste.
The jury is out whether this topic's complaint is a false
negativepositive or not (your other systems may have intercepted whatever URI-fingering MBAM actually picked up), but while I rate MalwareBytes highly (well, the last time I thought I might need it I did) I know there's no single answer. And McAfee/Norton have more often been the problem in years past. (Like almost a whole university department needed me to help remove a nasty rootkit installed alongside a "Watch the World Cup for free!" BHO/menu-bar trojan thing a few years back that got entirely past whichever 'big name' all-bells'n'whistles AV it was that the Uni had plumped for. Probably every other faculty too, but they were officially someone elses' problems.)
My rule of thumb: Stay away from the big guns (those two, primarily, others on advisement and according to recent experience/info) and preferably avoid any AV whose name
starts with "A" (and especially "AV") as 'too obvious'. But that's just in my particular circumstances, probably not advice I'd give to anyone else, totally out of context.
[1] And only via sneakernet from protected machines.
[2] Yearly? Not as frequent as monthly, and don't think it's quarterly, so it's probably annual.