aBlocks <= 2.17.0 - Authenticated (Contributor+) Privilege Escalation to 'roleSlug' Block Attribute

The aBlocks – Gutenberg Blocks, User Dashboard Builder, Popup Builder, Form Builder & Animation Builder plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 2.17.0 via the /ablocks/v1/form-builder/registration REST endpoint. The vulnerability exists because the endpoint is registered with permission_callback => __return_true and the register() handler reads roleSlug directly from attacker-controlled block attributes in post_content without ever verifying that the block's formType is registration — a condition that RegistrationFormSanitizer::verify() imposes only at save-time, meaning a Contributor can preserve an arbitrary roleSlug by saving a block with formType='login' and then triggering the endpoint via a valid wp_rest nonce and post-ownership check. This makes it possible for authenticated attackers, with Contributor-level access and above, to escalate their WordPress role to Editor or any other non-administrator role and receive a fully authenticated session at the elevated privilege level via WP_User::set_role() and wp_set_auth_cookie(). Escalation is bounded below administrator-tier roles because is_safe_registration_role() rejects any role holding manage_options, edit_users, delete_users, create_users, promote_users, or edit_theme_options, meaning the highest practically reachable role on a standard WordPress installation is Editor.