CVE-2026-16587 in Advanced Form Integration Plugin
Summary
by MITRE • 07/28/2026
The Advanced Form Integration — Connect Forms to 200+ Apps plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 2.6.0. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to overwrite the site's stored MailUp OAuth tokens in the adfoin_mailup_keys option with attacker-controlled tokens, hijacking future form-submission data to a MailUp account they control or nulling the tokens to break the integration entirely. This is exploitable by any authenticated user who can reach /wp-admin/profile.php, as admin_init fires for all logged-in users visiting any wp-admin page.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 07/28/2026
The Advanced Form Integration plugin for WordPress represents a critical security vulnerability that undermines the integrity of user authentication mechanisms within the WordPress ecosystem. This vulnerability affects all versions up to and including 2.6.0, creating a significant risk for WordPress sites that rely on the plugin's functionality to connect forms with over 200 applications. The flaw manifests as an authorization bypass that allows malicious actors with subscriber-level access or higher to manipulate core system configurations without proper verification of their privileges.
The technical implementation of this vulnerability stems from inadequate access control validation within the plugin's codebase. Specifically, the plugin fails to properly verify user authorization levels when processing requests related to MailUp OAuth token management. The vulnerability exploits the fact that admin_init hooks execute for all logged-in users visiting WordPress administration pages, including profile.php. This design flaw creates an attack surface where authenticated users can manipulate the adfoin_mailup_keys option in the WordPress database, effectively allowing them to replace legitimate OAuth tokens with malicious ones controlled by the attacker.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to completely compromise the integration between WordPress forms and MailUp services. Once an attacker successfully overwrites the stored OAuth tokens, they gain the ability to intercept and redirect all future form submissions to a MailUp account they control, potentially accessing sensitive user data and personal information collected through web forms. Alternatively, attackers can nullify the existing tokens entirely, causing complete disruption of the integration while maintaining their unauthorized access to the system.
This vulnerability aligns with CWE-863, which addresses "Incorrect Authorization," and represents a clear violation of the principle of least privilege in cybersecurity practices. From an ATT&CK framework perspective, this weakness maps to T1078 Valid Accounts and T1566 Phishing, as attackers can leverage legitimate user accounts to escalate privileges and maintain persistent access to form integration functionalities. The exploitation requires minimal technical skill and leverages the inherent trust model of WordPress administration interfaces, making it particularly dangerous in environments where multiple users have varying levels of administrative access.
Organizations should immediately implement mitigation strategies including updating to the latest plugin version if available, restricting user capabilities through role-based access controls, and monitoring for unauthorized changes to critical system options. Additionally, administrators should consider implementing network-level restrictions on access to wp-admin pages and establishing regular audits of stored OAuth tokens to detect potential compromise. The vulnerability demonstrates the critical importance of proper input validation and authorization checks in web applications, particularly those handling sensitive integration credentials that could provide attackers with extended access to user data and third-party services.