Hello,

This actually sounds like a bit of a theme issue. It is pretty standard in a WordPress theme that when you register your sidebar you want to have the “before_widget” argument contain the ID of the current widget and standard classes in the markup.

Also note that when you call register_sidebar in your theme to setup the sidebar, if you don’t override the “before_sidebar” argument, WordPress already does this for you by default.

So, this means that in your theme when the sidebar is registered, the theme author has (a) passed in their own “before_widget” argument and (b) didn’t include the id="%1$s" part.

For example, if you were you to call register_sidebar() with no arguments passed in, WordPress will use the following arguments by default:

$args = array(
	'name'          => __( 'Sidebar name', 'theme_text_domain' ),
	'id'            => 'unique-sidebar-id',
	'description'   => '',
	'class'         => '',
	'before_widget' => '<li id="%1$s" class="widget %2$s">',
	'after_widget'  => '</li>',
	'before_title'  => '<h2 class="widgettitle">',
	'after_title'   => '</h2>'
);

If you want to adjust the “before_widget” and “after_widget” markup in a theme, that’s totally fine, but just make sure that you always include the ID and standard classes in the surrounding markup something like this:

$args = array(
	'name'          => __( 'Your Sidebar', 'theme_text_domain' ),
	'id'            => 'your-sidebar',
	'before_widget' => '<aside id="%1$s" class="widget %2$s">',
	'after_widget'  => '</aside>'
);
register_sidebar( $args );

This will ensure that widget plugins out there that rely on $before_widget parameter when displaying the widget will work more consistently with your theme.