Bad JS can make it impossible to disable a broken hack.

[shaneargo]

If you create a hack that breaks the drop down menus, it becomes impossible to open the drop down to disable the broken hack, thus making it impossible to fix.

Two possible solutions are:

1. Have a kill switch which disables all enabled hacks. Make sure the button is accessible without javascript.
2. Do not inject hacks into the JS Hack configuration pages.

[shaneargo]

Fixed by commit 1503ef3 which enables the administrator to suspend injection with the click of a button.

Also fixed by commit d061b7c which automatically restricts injection to pages outside of JS Hack, allowing you to disable an offending packaged even if the dropdowns would otherwise be broken.