CVE-2023-6520 is a Cross-Site Request Forgery (CSRF) vulnerability affecting the WP 2FA – Two-factor authentication for WordPress plugin developed by melapress. This vulnerability exists in all versions up to and including 2.5.0. The root cause is improper nonce validation in the send_backup_codes_email function. Specifically, while a nonce check is implemented, it is only performed if a nonce is present in the request. An attacker can exploit this by omitting the nonce entirely, thereby bypassing the validation. This flaw allows an unauthenticated attacker to craft a malicious request that, when a site administrator or any registered user is tricked into clicking (e.g., via a phishing link), causes the system to send emails containing arbitrary content to registered users. This could be leveraged for phishing campaigns, social engineering, or spreading misinformation within the user base. The vulnerability does not allow direct compromise of credentials or site control but can undermine user trust and facilitate further attacks. The CVSS v3.1 base score is 4.3 (medium severity), reflecting the lack of confidentiality or availability impact but acknowledging the integrity impact and the requirement for user interaction. No known exploits are currently reported in the wild, and no patches have been linked yet, indicating that mitigation may rely on vendor updates or manual workarounds.

For European organizations using WordPress sites with the vulnerable WP 2FA plugin, this vulnerability poses a risk primarily to the integrity of communications and user trust. Attackers could send forged emails to registered users, potentially leading to phishing attacks or social engineering that could compromise user credentials or lead to further exploitation. Although the vulnerability does not directly expose sensitive data or allow system takeover, the indirect consequences could be significant, especially for organizations relying on WordPress for customer engagement, internal portals, or e-commerce. In sectors such as finance, healthcare, or government within Europe, where trust and secure communication are critical, this vulnerability could facilitate targeted attacks against employees or customers. The requirement for user interaction (clicking a malicious link) somewhat limits the attack scope but does not eliminate risk, especially in environments where users may be less security-aware. Additionally, the vulnerability could be exploited to disrupt normal operations by flooding users with unsolicited emails, potentially leading to reputational damage and increased support costs.

European organizations should prioritize the following mitigation steps: 1) Immediately check if their WordPress installations use the WP 2FA plugin version 2.5.0 or earlier and plan for an upgrade once a patched version is released by melapress. 2) Until a patch is available, implement web application firewall (WAF) rules to detect and block suspicious POST requests to the send_backup_codes_email endpoint, especially those missing nonce parameters. 3) Educate administrators and registered users about the risk of clicking unsolicited or unexpected links, emphasizing caution with emails that prompt actions related to two-factor authentication or account recovery. 4) Monitor outgoing email logs for unusual activity that could indicate exploitation attempts. 5) Consider disabling the send_backup_codes_email functionality temporarily if feasible, or restrict access to trusted IP ranges. 6) Employ Content Security Policy (CSP) headers and anti-CSRF tokens in custom integrations to reduce the risk of CSRF attacks. 7) Maintain regular backups and incident response plans to quickly address any phishing or social engineering incidents stemming from this vulnerability.