CVE-2018-5667 in read-and-understood Plugin
Summary
by MITRE
An issue was discovered in the read-and-understood plugin 2.1 for WordPress. XSS exists via the wp-admin/options-general.php rnu_username_validation_pattern parameter.
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Analysis
by VulDB Data Team • 12/23/2019
The vulnerability identified as CVE-2018-5667 resides within the read-and-understood plugin version 2.1 for WordPress, representing a cross-site scripting flaw that compromises the security integrity of WordPress administrative interfaces. This issue specifically manifests through the wp-admin/options-general.php page where the rnu_username_validation_pattern parameter fails to properly sanitize user input, creating an exploitable vector for malicious actors to inject arbitrary script code into the application's response. The vulnerability stems from inadequate input validation and output escaping mechanisms within the plugin's handling of administrative configuration parameters, allowing attackers to manipulate the username validation pattern field without proper security controls.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input containing script tags or other executable code within the rnu_username_validation_pattern parameter. When this malformed input is processed by the plugin and subsequently rendered in the WordPress admin interface, the browser executes the embedded malicious code, potentially enabling session hijacking, credential theft, or further compromise of the affected WordPress installation. This type of vulnerability directly maps to CWE-79 which categorizes cross-site scripting flaws as weaknesses in input validation and output encoding. The flaw represents a classic case of insufficient sanitization where user-supplied data flows directly into the application's output without proper HTML escaping or context-appropriate encoding, making it particularly dangerous within the privileged WordPress admin environment where attackers can leverage the executed code for broader system compromise.
The operational impact of CVE-2018-5667 extends beyond simple script execution as it provides attackers with potential access to sensitive administrative functions within WordPress. An attacker who successfully exploits this vulnerability could manipulate user validation patterns to redirect legitimate users to malicious sites, steal administrator session cookies, or even modify plugin configurations that could persist across multiple user sessions. The vulnerability's location within the general options page means that any user with sufficient privileges to access the WordPress admin panel could be targeted, though typically this would require at least contributor-level access or higher. This flaw significantly weakens the security posture of affected WordPress installations, particularly when combined with other vulnerabilities or when the plugin is used in environments where multiple users have administrative access. The vulnerability aligns with ATT&CK technique T1059.007 which covers the use of script-based attacks and T1566 which involves the delivery of malicious payloads through web applications.
Mitigation strategies for CVE-2018-5667 should prioritize immediate plugin updates to versions that address the XSS vulnerability through proper input sanitization and output escaping. Administrators should implement comprehensive input validation that filters out potentially malicious characters and ensures that all user-supplied data is properly escaped before rendering in HTML contexts. The recommended remediation includes applying the vendor-supplied patch or upgrading to a patched version of the read-and-understood plugin, while also implementing web application firewall rules that can detect and block suspicious patterns in the rnu_username_validation_pattern parameter. Additionally, organizations should conduct regular security audits of installed WordPress plugins to identify and remediate similar vulnerabilities, implement proper access controls to limit administrative privileges, and establish monitoring procedures to detect unauthorized changes to plugin configurations. The vulnerability serves as a reminder of the critical importance of input validation and output encoding practices in web applications, particularly in administrative interfaces where the potential impact of XSS attacks can be severe.