Today I found a strange ugly bug when I was scrolling to my questions.
"Next privilege" card was open and I scrolled at bottom and saw that card overlapping the header. It is for all the pop ups available, Next badge, latest badge, etc.
OS: Ubuntu - 16.04 (Xenial Xerus)
Browser: Chrome - version 59.0.3071.86 (official build) (64-bit)
Zoom size: 100% (default)
If "z-index:1" added to pop up box, it is being resolved.
See the images below.