Import and export users and customers < 2.0 - Privilege Escalation to Administrator via save_extra_user_profile_fields

Description

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.