CVE-2021-24429 in Salon Booking System Plugin
Summary
by MITRE • 07/13/2021
The Salon booking system WordPress plugin before 6.3.1 does not properly sanitise and escape the First Name field when booking an appointment, allowing low privilege users such as subscriber to set JavaScript in them, leading to a Stored Cross-Site Scripting (XSS) vulnerability. The Payload will then be triggered when an admin visits the "Calendar" page and the malicious script is executed in the admin context.
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Analysis
by VulDB Data Team • 07/15/2021
The CVE-2021-24429 vulnerability affects the Salon booking system WordPress plugin version 6.3.1 and earlier, representing a critical stored cross-site scripting flaw that undermines the security of web applications. This vulnerability stems from inadequate input validation and sanitization practices within the plugin's handling of user-submitted data, specifically the First Name field during appointment booking processes. The flaw allows low-privilege users such as subscribers to inject malicious JavaScript code that persists in the application's database and executes when administrators view appointment data through the calendar interface.
The technical implementation of this vulnerability resides in the plugin's failure to properly sanitize and escape user input before storing it in the database and rendering it in administrative interfaces. When a subscriber submits an appointment with malicious JavaScript in the First Name field, the plugin accepts this input without adequate filtering or encoding, storing the payload in the backend database. Subsequently, when administrators access the calendar page to view appointment details, the stored JavaScript code is rendered in the browser context without proper output escaping, creating an ideal environment for cross-site scripting attacks.
This vulnerability operates under the Common Weakness Enumeration CWE-79 category, specifically addressing stored XSS conditions where malicious scripts are permanently stored on the target server and executed whenever users access the compromised data. The attack vector is particularly concerning as it requires minimal privileges for exploitation, leveraging the low-privilege subscriber account to compromise the higher-privilege administrator account. The execution context of the malicious script runs with administrative privileges, potentially allowing attackers to escalate their access, steal session cookies, modify appointment data, or even execute arbitrary commands within the WordPress environment.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it provides attackers with persistent access to administrative functions and sensitive appointment data. Administrators who regularly visit the calendar page become unwitting victims of the stored payload execution, creating a continuous attack surface that remains active until the vulnerability is patched. The vulnerability also aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: JavaScript, where attackers leverage browser-based scripting capabilities to maintain persistent access and execute malicious code within the administrative context.
Mitigation strategies should prioritize immediate plugin updates to version 6.3.1 or later, which contain the necessary sanitization patches. Additionally, administrators should implement proper input validation at multiple layers, including client-side and server-side filtering, and ensure that all user-submitted data undergoes proper HTML escaping before database storage and presentation. Network-level monitoring should be enhanced to detect anomalous JavaScript payloads in form submissions, while regular security audits should verify that all WordPress plugins maintain proper sanitization practices. Organizations should also consider implementing content security policies to limit the execution of inline scripts and restrict the potential impact of such stored XSS vulnerabilities.