CVE-2021-25083 in Registrations for the Events Calendar Plugin
Summary
by MITRE • 01/24/2022
The Registrations for the Events Calendar WordPress plugin before 2.7.10 does not escape the qtype parameter before outputting it back in an attribute in the settings page, leading to a Reflected Cross-Site Scripting
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Analysis
by VulDB Data Team • 01/28/2022
The vulnerability identified as CVE-2021-25083 affects the Registrations for the Events Calendar WordPress plugin, specifically versions prior to 2.7.10. This issue represents a classic reflected cross-site scripting vulnerability that arises from improper input sanitization within the plugin's administrative settings interface. The flaw manifests when the plugin fails to properly escape the qtype parameter before rendering it back into an HTML attribute on the settings page, creating an avenue for malicious actors to inject arbitrary JavaScript code.
The technical exploitation of this vulnerability occurs through the manipulation of the qtype parameter within the plugin's settings page URL. When a user with administrative privileges navigates to the affected settings page with a maliciously crafted qtype value, the plugin outputs this parameter directly into an HTML attribute without appropriate escaping mechanisms. This allows attackers to inject malicious scripts that execute in the context of the victim's browser session, potentially leading to unauthorized actions performed on behalf of the authenticated user.
From an operational perspective, this vulnerability poses significant risks to WordPress sites utilizing the affected plugin version. The reflected nature of the XSS means that attackers can craft specific URLs containing malicious payloads that, when clicked by an administrator, would execute the injected code in the administrator's browser. This could enable attackers to steal session cookies, perform unauthorized administrative actions, modify plugin settings, or even gain full control over the affected WordPress installation. The vulnerability is particularly dangerous because it requires minimal user interaction beyond visiting a malicious link, and the administrative context provides elevated privileges that can be exploited for further compromise.
The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in software applications. This classification indicates that the issue stems from the application's failure to sanitize user input before incorporating it into dynamically generated content. The ATT&CK framework categorizes this type of vulnerability under T1566, specifically the technique of "Phishing with Social Engineering," as attackers can craft convincing phishing campaigns targeting administrators with malicious links that exploit this XSS flaw. Additionally, the vulnerability demonstrates characteristics of T1059, where adversaries leverage command and control channels through malicious script execution, potentially enabling further malicious activities such as data exfiltration or lateral movement within the compromised environment.
Organizations should immediately update to version 2.7.10 or later of the Registrations for the Events Calendar plugin to remediate this vulnerability. The patch addresses the root cause by implementing proper input sanitization and output escaping mechanisms for the qtype parameter. Administrators should also consider implementing additional security measures such as content security policies, regular security audits, and monitoring for suspicious administrative activity. The vulnerability serves as a reminder of the critical importance of input validation and output escaping in web applications, particularly in administrative interfaces where elevated privileges can be exploited to cause significant damage.