CVE-2026-118185 in Security Optimizer Plugin
Summary
by MITRE • 10/31/2026
The Security Optimizer WordPress plugin before 1.6.9 does not limit the number of two-factor authentication codes that can be submitted for a pending login, allowing an attacker who already knows a user's password to brute force the second factor and take over the account.
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Analysis
by VulDB Data Team • 10/31/2026
The vulnerability identified in Security Optimizer versions prior to 1.6.9 represents a critical failure in access control mechanisms specifically related to multi-factor authentication enforcement. While two-factor authentication is widely regarded as an essential layer of defense against credential theft, its effectiveness relies heavily on the implementation details of the verification process. In this specific instance, the plugin fails to implement rate limiting or account lockout policies for the second factor input field. This architectural oversight means that once a user initiates a login sequence by entering their username and password, the system enters a pending state where it awaits the one-time passcode from the authenticator app or SMS service. During this window, there is no cap on the number of attempts an attacker can make to guess the correct code.
From a technical perspective, this flaw constitutes a classic brute force attack vector applied to time-based one-time passwords. Most modern two-factor authentication systems generate codes that are numeric and relatively short in length, typically six digits long. This results in only ten thousand possible combinations per cycle. Without rate limiting, an automated script can iterate through all potential permutations rapidly. The attacker does not need to crack the user's password or intercept the communication channel; they simply require knowledge of the valid username and have triggered a login attempt by knowing when the victim is likely to be active online. This transforms what should be a secure second factor into a trivially guessable value, effectively nullifying the security benefit provided by two-factor authentication in this context.
The operational impact of this vulnerability is severe for any organization or individual relying on Security Optimizer for access protection. An attacker who has obtained user credentials through phishing, credential stuffing from other breaches, or simple password guessing can proceed to compromise the account with high probability and minimal effort. This leads directly to unauthorized access, data exfiltration, and potential lateral movement within a network if the compromised account holds administrative privileges. For WordPress sites, this often means full control over the content management system, allowing for defacement, malware injection, or further exploitation of other plugins and themes installed on the server. The risk is amplified because many users may reuse passwords across multiple services, increasing the likelihood that an attacker possesses valid credentials from a previous incident.
This vulnerability aligns with CWE-307, which describes Improper Restriction of Excessive Authentication Attempts. It also maps to MITRE ATT&CK technique T1110.001, specifically Brute Force: Password Guessing for Web Applications. The failure lies not in the cryptographic strength of the two-factor codes themselves but in the lack of procedural controls to limit interaction with the authentication endpoint. To mitigate this issue, administrators must upgrade Security Optimizer to version 1.6.9 or later where these limits are enforced. In environments where immediate patching is not feasible, temporary mitigations include implementing web application firewall rules that detect and block rapid successive login attempts for specific usernames regardless of the factor being validated. Additionally, enforcing strong password policies reduces the likelihood of initial credential compromise, thereby reducing the attack surface available to potential adversaries seeking to exploit this secondary weakness.