Now this is weird. I am sure many of us are facing this. it goes like this
Select the eye dropper tool
pick a color
Fill it wherever you want
Switch to another tool. Say the "Pick' Tool
and here comes a square box on the document. A small Square box which refuses to disappear come what may. It does not harm the document. It does not print nor does it come in the jpg if you export to JPG. But it is visible and it is irritating.
Ah yes it vanishes once you close the document and reopen.
Now is this a bug or whatever. But man it gets on my nerves.
OK, folks in this thread. Try this to see if it consistently reproduces the problem on your systems. It does on mine.
You can then try repeating the procedure with the following change: For Step 5, move the cursor completely off of Shape B before using the Space Bar to activate the Pick Tool. On my system, this does not produce the "ghost square".
For something different, you could also try repeating the procedure as originally described above, but with the following change: For Step 4, apply the sampled color to the outline of Shape B. On my system, that leaves behind an outlined but unfilled "ghost box".
On my system, activating the Eyedropper tool again causes the "ghost" shape to disappear.
Trying this some more, I find that I get this if I sample a color with the Eyedropper, then, at any time that the "sampled color square" or "sampled color box" is visible by the cursor, switch to some other tool (e.g., Pick Tool, Freehand Tool, Text Tool).