I just found a bug introduced in one of your last releases.
Open a table with some data inside, swith e.g. to the Data tab, select first cell by clicking on it, hold Ctrl and then click on third cell in the same column. Two cells should be selected. Pres Ctrl + C to copy the content of those cells, paste the content somewhere -> you copied all three cells. In other words you will copy everything between the first selected cell and the last selected cell (like if you would hold Shift key while selecting those cells).
I can confirm that this is a bug. It seems to be an issue for selections in one column. The copy and paste functionality has been extended significantly and can only apologise that this slipped though.
I'll raise a bug and paste details here.
I have raised and fixed the following bug: Bug 15862196 - COPY OF MULTI-SELECTION IN SINGLE COLUMN COPIES ALL CELL BETWEEN FIRST AND LAST
The fix should be available in the next major release of SQLDeveloper or patch (should there be one) of 3.2.20.09.87.