I had over 160 alerts... (It might have been 360 actually, anyway it was a ridiculously large number that was 3 digits long). Selected the alerts tab, turns out all but 3 were invalid.
It wasn't a hack. It was just a spammer. XenForo has great spam management tools. You can never stop 100% of spam though because it would create a bad user experience and plus sometimes spammers aren't doing it programmatically. Plus sometimes it's legitimately a person sitting there for hours, wasting their time.
It was only 6:04 AM for Brogan when Jake posted, though it was still 10:04 PM for Jake and me. However, it wouldn't have really surprised me if Brogan had gotten it, because, according to him, sleep is for the weak. Ain't that right, @Brogan?