Possible invalid user roles count with similarly named roles

[layotte]

How to replicate: Create a user role named "custom_administrator", add users to this role. Role count in /wp-admin/users.php for the "Administrator" role will include the users in the "custom_administrator" role.

Currently line 852 of /wp-includes/users.php counts the roles with this line:

$select_count[] = "COUNT(NULLIF(`meta_value` LIKE '%" . like_escape($this_role) . "%', FALSE))";

Lines in DB look like this:

a:1:{s:13:"administrator";s:1:"1";}
a:1:{s:20:"custom_administrator";s:1:"1";}

Patch for users.php attached, to this:

$select_count[] = "COUNT(NULLIF(`meta_value` LIKE '%\"" . like_escape($this_role) . "\"%', FALSE))";

Related: #12693

Fixed in [19735].