This has been reported on Sencha forums. Hopefully support or a Javascript expert here can find a solution.
The problem is that tabbing (Tab key on keyboard) through the fields is not restricted to the modal window only.
After you tab through the fields in the modal window, instead of focus shifting back to the 1st field, you now tab through the fields behind the the modal, through the custom or standard links and buttons you may have in your visual perspective.
Not only that, all these buttons and links can be executed by pressing space or enter key while the modal is open. These links and buttons could be anything.
This presents a bigger problem that just being an annoying UI issue.
After you tab through all the fields, in most cases, the form buttons are not focused on next either (see below).
The tabbing needs to be restricted to the modal and the modal buttons.
Possible solution:
http://forums.ext.net/showthread.php?12238-CLOSED-1-0-Modal-window-tabindex
Few Sencha forum posts:
http://www.sencha.com/forum/showthread.php?257014-tabindex-and-modal-window
http://forums.ext.net/showthread.php?12238-CLOSED-1-0-Modal-window-tabindex
http://www.sencha.com/forum/showthread.php?146062
http://www.sencha.com/forum/showthread.php?247869-modal-window-and-tabindex
