Widgets might get null bytes in their CSS class

[qualipsoft]

When register_sidebar_widget is called with a lambda/create_function as output_callback and no/empty classname, the widget's CSS class will contain "\0lamba_123" (\0 being the null character and 123 being the actual assigned lamba id).

This bug was introduced in 2.3 by #4910 (In [6098]).

The simple fix might be to left-trim null bytes from the classname (this would fix the case for lambda's, and maybe other cases I'm not aware of)

The patch looks ok, but I don't know if it's worth fixing, since you should be using the new WP_Widget class, instead of setting each handler manually.

Scribu is right, support for 'old style' wigets is currently deprecated will probably be removed in 3.0.