CVE-2021-24406 in wpForo Forum Plugin
Summary
by MITRE • 07/06/2021
The wpForo Forum WordPress plugin before 1.9.7 did not validate the redirect_to parameter in the login form of the forum, leading to an open redirect issue after a successful login. Such issue could allow an attacker to induce a user to use a login URL redirecting to a website under their control and being a replica of the legitimate one, asking them to re-enter their credentials (which will then in the attacker hands)
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Analysis
by VulDB Data Team • 07/09/2021
The wpForo Forum WordPress plugin version 1.9.6 and earlier contained a critical security vulnerability that enabled open redirect attacks through improper input validation. This flaw specifically affected the login form functionality where the plugin failed to properly sanitize or validate the redirect_to parameter that users could provide during the authentication process. The vulnerability existed within the plugin's authentication flow and represented a significant weakness in the access control mechanisms of the forum system.
The technical implementation of this vulnerability stemmed from the plugin's lack of proper parameter validation in the login handler. When users accessed the forum login page, they could supply a redirect_to URL parameter that would be used to redirect them after successful authentication. The plugin's code did not validate whether this redirect target was within the legitimate domain of the forum installation, allowing attackers to craft malicious login URLs with redirect parameters pointing to attacker-controlled domains. This validation failure created an environment where the plugin would blindly accept and execute any redirect URL provided by the user.
The operational impact of this vulnerability was severe and directly enabled credential theft through social engineering attacks. Attackers could construct deceptive login URLs that appeared legitimate to forum users, redirecting them to phishing pages that mimicked the actual forum interface. When users entered their credentials on these malicious pages, the attacker would capture the authentication information and gain unauthorized access to user accounts. This attack vector specifically aligned with the tactics described in the attack pattern taxonomy under the MITRE ATT&CK framework for credential access and phishing techniques. The vulnerability also enabled broader security implications including potential account takeover and data compromise.
This particular vulnerability can be classified as a variant of the common weakness enumeration CWE-601, which specifically addresses open redirect vulnerabilities in web applications. The flaw represented a failure in input validation and output encoding practices that are fundamental to secure web application development. Organizations using vulnerable versions of the wpForo plugin faced significant risk of user credential compromise and unauthorized account access. The security implications extended beyond simple credential theft to potentially enable further attacks including privilege escalation and data exfiltration from compromised accounts.
The recommended mitigation for this vulnerability involved upgrading to wpForo plugin version 1.9.7 or later, which contained the necessary fixes to properly validate redirect URLs. Administrators should also implement additional security measures including monitoring for suspicious login patterns, implementing multi-factor authentication for forum accounts, and educating users about the dangers of clicking suspicious links. Network security controls such as web application firewalls and URL filtering systems could provide additional protection layers, though the primary remediation remained the plugin upgrade. Organizations should also conduct thorough security assessments of their WordPress installations to identify and address similar validation weaknesses in other plugins or custom code components.