The User Profile Builder – Beautiful User Registration Forms, User Profiles & User Role Editor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Avatar Field in all versions up to, and including, 4.0.2 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The zero-length multipart file branch in wppb_save_avatar_value() writes the raw request value directly to user meta, bypassing the wppb_save_attachment_id()/wppb_verify_attachment_id() validation path; the stored payload is later adopted as a WordPress attachment URL and rendered unescaped by wppb_default_fields_make_upload_button() when an administrator views the affected account.