Quite annoying and rather a show-stopper for using big cursors. Steps to reproduce: 1) set mouse cursor theme so that the cursor is 32 or 48 pixels big (bigger than 16 px) -- Settings/Mouse and Touchpad/Theme/Vanilla-DMZ (or e.g. whiteglass) and Cursor size=32 or 48 2) try to drag a file/folder around on the desktop - or - in file manager window try to drag a file to folder. As soon as a square indicating the target of the drag appears, the mouse cursor gets corrupted. Reproducible always, does not occur as long as the cursor size is 16px. Seems like those 16pixels are hard coded somewhere. Once the cursor is corrupted, only restart of X will put it back to normal (Settings/Mouse and Touchpad/Theme incurs changes, but the cursor stays corrupted).
Strangely enough, when trying to make a screenshot, gimp returns correct image... Perhaps the bug is somewhere else (Xorg driver?)
Just got the corruption in Firefox too when dragging picture (mostly it works, but from time to time corruption occurs). So this is not a thunar bug.