Shift+left arrow key from single selecion before multimeasure rest leads to range selection up to end of score
A standard way to select a range is to click one note or rest, hold down the Shift key, and use the right or left arrow key to extend the selection. (I'm all the more likely to do this because holding down Shift and clicking not exactly on a note head now leads to a multiple note selection, not a range selection—perhaps something I should file an additional bug report for? Never mind for now.)
However, in MuseScore 2, if the initial note or rest is just before a multimeasure rest, attempting to select to the left—that is, holding down Shift and hitting the left arrow—actually ends up selecting the entire score to the right.
Note that this does not apply if the initial note or rest is already selected as a range selection. To reproduce, you may wish to hit Escape a couple of times before clicking on the note or rest.