Exploit
In video games, an exploit is the use of a bug or glitches, game system, rates, hit boxes, speed or level design etc. by a player to their advantage in a manner not intended by the game's designers.Exploits have been classified as a form of cheating; however, the precise determination of what is or is not considered an exploit can be controversial. This debate stems from a number of factors but typically involves the argument that the issues are part of the game and require no changes or external programs to take advantage of them,
-wikipedia
bug
A software bug is an error, flaw or fault in a computer program or system that causes it to produce an incorrect or unexpected result, or to behave in unintended ways.
-wikipedia
So by this definition we all can say that is bug and that what MS did is exploit. Unless this is intended small place where ppl can jump next to the wall then MS is clear and we qq w/o any reasen