What do you think iter++ is doing in the loop body? Hint: look at the loop increment section (++itr) does anything look similar? You need to realize that an iterator has similarities to a pointer. When you increment the non-dereferenced iterator you're incrementing the iterator not modifying the values the iterator is pointing to.
By the way if you're using C++11 or higher standard code you can simplify the above to something like:
for(auto& itr : scores)
Which should increase the value held in each element of your vector.
Assuming that you define vector<int> scores and put this in a program, it compiles and runs.
Whether something is "wrong" with it depends on what it's supposed to do. One odd thing is that it increments the iterator twice: once as the last part of the for() statement and once inside the body of the loop.