User Frontend <= 4.3.13 - Authenticated (Subscriber+) Privilege Escalation via post_content Parameter

Overview

The User Frontend – Membership, User Registration, User Profile, User Directory & Content Restriction with Frontend Post Submission plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 4.3.13 via the post_content parameter of the submit_post() function. The vulnerability exists because the protected-shortcode blocklist guard inspects the sanitize_textarea_field() copy of the submitted post_content, while the copy actually persisted to the database is processed through wp_kses(), whose wp_kses_no_null() step strips C0 control bytes — allowing an attacker to inject a single \x01 byte inside the [wpuf-registration] tag name to defeat the strpos() blocklist check while the clean, functional shortcode is stored verbatim; strip_shortcodes() does not neutralize the stored shortcode either, because the Frontend container that registers it via add_shortcode() is only instantiated when is_admin() is false, and admin-ajax requests have is_admin() === true. This makes it possible for authenticated attackers, with Subscriber-level access and above, to inject a [wpuf-registration role="editor"] shortcode into a published post, causing a live Editor-role registration form to be rendered publicly on the frontend that any visitor — or the attacker themselves — can submit to mint a WordPress Editor account with an immediately active privileged session when the default autologin_after_registration setting is enabled.

Affected

• user_frontend_membership_user_registration_user_profile_user_directory_content_restriction_with_frontend_post_submission <= 4.3.13

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.