How do I suppress firefox password field completion?

From Mozilla's documentation

<form name="form1" id="form1" method="post" autocomplete="off"
  action="http://www.example.com/form.cgi">
[...]
</form>

http://developer.mozilla.org/en/How_to_Turn_Off_Form_Autocompletion

Have you tried adding the autocomplete="off" attribute in the input tag? Not sure if it'll work, but it is worth a try.

The autocomplete="off" method doesn't work for me. I realized firefox was injecting the saved password in the first password field it encountered, so the solution that worked for me was to create a dummy password field before the password update field and hide it. Like so:

<input type="password" style="display: none;" />
<input type="password" name="password_update" />