5.7.5.1 fixes a number of important bugs in 5.7.5, especially for those users running PHP 5.3.8 and earlier, or running MySQL in strict mode. It is a maintenance release and is recommended for all users of concrete5.7.
If you haven't upgraded to concrete5 5.7.5 yet now is a perfect opportunity to do so. See what's new in 5.7.5.