I have been running into this issue more and more lately during pentests.

Network Appliances with web interfaces where a client-side javascript mangles the login credentials before posting. I haven't been able to locate a tool capable of bruteforcing logins in this situation. I have written a script on a few occasions to deal with the issue, but I can't help, but think that someone might have addressed this issue.

What say the hivemind, is there something out there I could be using to make my pentests more efficient?