CVE-2026-89080 in Really Simple Security Plugin
Summary
by MITRE • 09/13/2026
The Really Simple Security WordPress plugin before 9.8.1 does not prevent an unauthenticated request from resetting an account's completed email two-factor enrolment, allowing an attacker who already knows the account's password to bypass the second factor and obtain that user's session, up to administrator.
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Analysis
by VulDB Data Team • 09/13/2026
The Really Simple Security plugin for WordPress is a widely utilized security enhancement tool designed to harden website configurations by implementing features such as two-factor authentication, login limits, and malware scanning. Version 9.8.1 introduced critical fixes regarding the integrity of multi-factor authentication workflows. Prior to this version, the application logic governing the management of user security settings contained a significant flaw in how it handled requests related to email-based two-factor enrollment status. Specifically, the plugin failed to enforce proper authorization checks on endpoints responsible for updating or resetting the completed state of an account's two-factor authentication configuration. This lack of validation allowed any actor with network access to interact directly with these internal API functions without requiring a valid session token or administrative privileges at the time of the request.
The technical core of this vulnerability lies in the absence of strict input validation and privilege verification for actions that modify security-critical user attributes. When an unauthenticated HTTP request is sent to reset the completed email two-factor enrollment flag, the server processes it as a legitimate instruction from the currently logged-in user or assumes default permissions without verifying if the requester actually holds those rights. This design oversight creates a path where an attacker who has already obtained valid credentials for a specific account through phishing, credential stuffing, or other means can manipulate the security state of that account remotely. By resetting the enrollment status to incomplete or nullifying the two-factor requirement, the attacker effectively strips away the second layer of defense intended by the site administrator and end user.
The operational impact of this vulnerability is severe because it directly undermines the primary purpose of implementing multi-factor authentication. Once an attacker possesses a valid username and password pair for any account on the target WordPress installation, they can execute a request to disable or reset the two-factor requirement. This action allows them to log in using only the known credentials without being prompted for the secondary code sent via email. Consequently, the attacker gains full access to the user session associated with that account. If the compromised account holds administrative privileges, which is common in many WordPress deployments due to initial setup practices or privilege escalation attacks, the attacker obtains complete control over the website. This includes the ability to modify site content, install malicious plugins, steal sensitive data from users and visitors, deface the public-facing interface, or use the server as a pivot point for further network intrusions.
This vulnerability aligns with CWE-284, which describes Improper Access Control, specifically where insufficient verification of user privileges allows unauthorized actions to be performed. It also maps to MITRE ATT&CK technique T1078, Valid Accounts, as the exploitation relies on using legitimate credentials combined with a flaw in authentication enforcement mechanisms. The scenario represents a classic case of broken access control leading to privilege escalation and session hijacking potential. To mitigate this risk, administrators must immediately update the Really Simple Security plugin to version 9.8.1 or later, where these authorization checks have been corrected. Additionally, organizations should enforce strict password policies to reduce the likelihood of credential compromise in the first place and consider implementing additional layers of security such as IP-based restrictions for administrative logins or hardware-based two-factor authentication methods that are less susceptible to software-level logic flaws. Regular auditing of plugin code for proper access control implementation is also recommended to prevent similar issues across other third-party extensions.