Cursed black box following cursor, on multiple Macs This is a bit of an odd one for me, I'm hoping someone here might have some advice. We have a couple mac users in the office, and a few of them have been reporting this box has been appearing sporadically. Any advice?

This is on a MBP 11,5, I've checked most of the accessibility settings, mouse settings, tried a different mouse, the issue still persists. 

EDIT: Still no luck, I haven't had a lot of time to troubleshoot but after messing with pretty much every accessibility setting I'm fairly convinced its not that, going to try a new monitor in a desperate attempt. 

EDIT 2: I haven't been able to find a solution to this issue, any help at all is greatly appreciated!
I have yosemite, and i found a setting that does what you're describing but does not look quite like yours, for me it creates a box AROUND the mouse.
So hopefully you dont have yosemite and thats why. Anyways you can find the setting in:

System preferences -&gt; Accesibility -&gt; Zoom -&gt; More Options


Then when you're here you should uncheck 'Show preview rectangle when zoomed out'. If its not checked, check and uncheck it for good measure.
Found here