It is better to ask for forgiveness than to ask for permission. If you see an issue that needs to be solved, by all means, take it, fix it, and then let your manager know that you’ve done it. That is, of course assuming that you’re acting with good intentions. I’ve found that managers generally prefer people who find problems, solve them on their own, and then demonstrate the results at the end.
If, for some reason, things do not go well, you can always ask for forgiveness. My experience has shown that is rarely necessary. It is best to assume that you have the authority to act, and do so decisively, rather than asking permission for every step. Try it- and see how well it works.