Of injuries in general, you see a good portion of hamstring injuries in weightlifting and powerlifting. You see some in CrossFit, but really, you see a lot more knee issues due to lack of hamstring development in typical CrossFit programming and technical focus.
And once you've injured your hamstring, the likelihood of re-injury is particularly high. This article outlines some very easy protocols to follow to help buttress your hamstring toughness to prevent initial injury or re-injury.
Some of the descriptions they use for body position aren't defined well, but just keep in mind as you try to interpret, all of these movements are meant to be eccentric: extending the hamstring with the added stress of resistance or body weight.
Happy Hamstrings = Happy Knees, Happy Hips, Happy Squats, Happy Life.