CVE-2023-6506 is a medium-severity vulnerability affecting the WP 2FA – Two-factor authentication for WordPress plugin developed by melapress, specifically versions up to and including 2.5.0. The vulnerability is classified as an Insecure Direct Object Reference (IDOR), identified under CWE-639, which involves authorization bypass through a user-controlled key. The flaw exists in the send_backup_codes_email functionality, where the plugin fails to properly validate a key parameter controlled by the user. This lack of validation allows an attacker with subscriber-level privileges—typically the lowest level of authenticated user in WordPress—to send backup code emails to arbitrary users on the site. Although the vulnerability does not directly compromise confidentiality or availability, it enables unauthorized actions that can be leveraged for social engineering or phishing attacks by sending emails impersonating the site or administrator. The CVSS v3.1 score is 4.3 (medium), reflecting that the attack vector is network-based, requires low privileges, no user interaction, and impacts integrity but not confidentiality or availability. No known exploits are currently reported in the wild, and no official patches are linked yet. This vulnerability highlights improper access control and insufficient validation of user-supplied input in a security-critical plugin component.

For European organizations using WordPress with the WP 2FA plugin, this vulnerability poses a risk primarily related to integrity and trust within the user community. An attacker with subscriber access could send unauthorized emails to other users, potentially facilitating phishing campaigns or social engineering attacks that could lead to credential theft or further compromise. While the vulnerability does not allow direct data leakage or system takeover, it undermines the security assurances provided by two-factor authentication mechanisms. Organizations in sectors with strict data protection regulations, such as finance, healthcare, or government, may face reputational damage and compliance risks if attackers exploit this flaw to deceive users or employees. Additionally, the ability to send arbitrary emails could be used to distribute malicious links or attachments, increasing the risk of malware infections. The impact is heightened in environments where subscriber accounts are easily created or compromised, such as public-facing websites with open registrations.

To mitigate this vulnerability, European organizations should: 1) Immediately review and restrict subscriber-level permissions to minimize the risk of exploitation. 2) Monitor outgoing emails for unusual activity, especially those related to backup codes or authentication processes. 3) Temporarily disable the send_backup_codes_email functionality if feasible until an official patch is released. 4) Apply strict input validation and access control checks on user-controlled parameters within the plugin code, ensuring keys are verified against the authenticated user's identity. 5) Educate users and administrators about the potential for phishing attempts originating from compromised subscriber accounts. 6) Regularly update the WP 2FA plugin once a patch addressing CVE-2023-6506 is available. 7) Employ additional email security measures such as SPF, DKIM, and DMARC to reduce the impact of unauthorized emails. 8) Consider implementing web application firewalls (WAFs) with rules to detect and block suspicious requests targeting the vulnerable endpoint.