CVE-2026-66634 Overview
CVE-2026-66634 is an Insecure Direct Object References (IDOR) vulnerability affecting the Modal Survey WordPress plugin in versions up to and including 2.0.2.2.3. The flaw allows authenticated users at the Subscriber role level to access or manipulate objects belonging to other users by supplying attacker-controlled identifiers to plugin endpoints. The weakness is categorized under CWE-639: Authorization Bypass Through User-Controlled Key. Successful exploitation results in unauthorized read access to data that should be restricted by the plugin's access control logic.
Critical Impact
Authenticated Subscriber-level attackers can bypass authorization checks in the Modal Survey plugin and access survey objects owned by other users, resulting in confidentiality loss.
Affected Products
- WordPress Modal Survey plugin versions <= 2.0.2.2.3
- WordPress sites with Subscriber-or-higher registration enabled
- Any deployment exposing the vulnerable plugin endpoints to authenticated users
Discovery Timeline
- 2026-08-18 - CVE-2026-66634 published to NVD
- 2026-08-20 - Last updated in NVD database
Technical Details for CVE-2026-66634
Vulnerability Analysis
The Modal Survey plugin fails to verify that the authenticated user requesting an object is authorized to access that specific object. The plugin accepts user-supplied identifiers, such as survey IDs or record keys, and returns the associated data without validating ownership or role-based permissions. An attacker holding a low-privilege Subscriber account can iterate through identifiers to enumerate survey data belonging to other users. The vulnerability is limited to confidentiality impact and does not permit modification of data or disruption of service. The attack requires network access and low privileges, with no user interaction required from the victim.
Root Cause
The root cause is a missing authorization check on object references passed through plugin request parameters. The plugin trusts the identifier submitted by the authenticated user and does not compare the requesting user against the object owner or an access control list. This pattern maps directly to CWE-639, where authorization decisions rely on a user-controlled key.
Attack Vector
An attacker registers or authenticates as a Subscriber, then sends crafted requests to the vulnerable plugin endpoint with modified object identifiers. Because the plugin does not enforce ownership checks, the server returns objects belonging to other users. Refer to the Patchstack Vulnerability Advisory for endpoint-level technical details. No verified proof-of-concept code is publicly available at the time of publication.
Detection Methods for CVE-2026-66634
Indicators of Compromise
- Unexpected requests to Modal Survey plugin endpoints from accounts with the Subscriber role.
- Sequential or enumerated object identifiers in query strings or POST bodies targeting the plugin.
- Elevated response volumes returned to low-privilege accounts that would not normally read survey data.
Detection Strategies
- Review WordPress access logs for repeated plugin requests from a single authenticated Subscriber account with varying id parameters.
- Correlate authentication events with plugin API calls to identify low-privilege accounts touching resources owned by other users.
- Baseline normal survey access patterns and alert on deviations tied to newly registered accounts.
Monitoring Recommendations
- Enable verbose logging on the WordPress site and forward logs to a centralized SIEM for correlation.
- Monitor for new Subscriber account creation immediately followed by plugin API activity.
- Track outbound data volumes from the WordPress host to detect bulk enumeration.
How to Mitigate CVE-2026-66634
Immediate Actions Required
- Identify all WordPress sites running the Modal Survey plugin and confirm the installed version.
- Restrict or disable new user registration on affected sites until a patched version is applied.
- Audit existing Subscriber accounts and remove those that are unknown or inactive.
Patch Information
At the time of publication, the Patchstack Vulnerability Advisory tracks this issue for versions <= 2.0.2.2.3. Administrators should consult the vendor advisory for the current fixed release and update the plugin as soon as a patched version becomes available.
Workarounds
- Deactivate the Modal Survey plugin on affected sites until a fixed version is installed.
- Apply a Web Application Firewall (WAF) rule that blocks Subscriber-authenticated requests to Modal Survey endpoints containing object identifiers the account does not own.
- Enforce the principle of least privilege by disabling open registration and restricting the Subscriber role from accessing plugin endpoints where feasible.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
