Import and export users and customers <= 1.29.7 - Privilege Escalation to Administrator via save_extra_user_profile_fields

The Import and export users and customers plugin for WordPress is vulnerable to privilege escalation in all versions up to, and including, 1.29.7. This is due to the 'save_extra_user_profile_fields' function not properly restricting which user meta keys can be updated via profile fields. The 'get_restricted_fields' method does not include sensitive meta keys such as 'wp_capabilities'. This makes it possible for unauthenticated attackers to escalate their privileges to Administrator by submitting a crafted registration request that sets the 'wp_capabilities' meta key. The vulnerability can only be exploited if the "Show fields in profile" setting is enabled and a CSV with a wp_capabilities column header has been previously imported.