CVE-2025-30540 Overview
CVE-2025-30540 is a stored cross-site scripting (XSS) vulnerability in the AvaiBook WordPress plugin. The flaw stems from improper neutralization of user input during web page generation, tracked as [CWE-79]. It affects all versions of AvaiBook up to and including version 1.2. An authenticated attacker with high privileges can inject persistent JavaScript payloads that execute in the browser context of any user who views the affected page. Successful exploitation requires user interaction and results in a scope change, allowing the attacker to impact resources beyond the vulnerable component.
Critical Impact
Stored XSS enables session hijacking, credential theft, and unauthorized actions performed in the context of authenticated WordPress users viewing the injected content.
Affected Products
- AvaiBook WordPress plugin — all versions up to and including 1.2
- WordPress installations with the AvaiBook plugin activated
- Downstream sites where administrators or editors render plugin-controlled content
Discovery Timeline
- 2025-03-24 - CVE-2025-30540 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-30540
Vulnerability Analysis
The AvaiBook plugin accepts user-supplied input and stores it without proper output encoding or input sanitization. When the stored data is later rendered in a web page, the browser interprets attacker-controlled markup as executable script. Because the payload persists in the database, every subsequent visitor to the affected page triggers the malicious script.
Exploitation requires an authenticated actor with elevated privileges within the WordPress site. The attacker also depends on victim interaction, such as viewing the injected page in an administrative or editorial context. The attack originates over the network against the vulnerable WordPress endpoint.
Root Cause
The root cause is missing or insufficient sanitization of input fields exposed by the AvaiBook plugin prior to storage, combined with the absence of contextual output encoding when the stored data is rendered in HTML responses. This aligns with the [CWE-79] weakness pattern.
Attack Vector
An attacker with a privileged WordPress account submits crafted input containing HTML or JavaScript through plugin-controlled fields. The payload is stored server-side and served to other users. When a victim loads the affected page, the browser executes the payload in the origin of the WordPress site, giving the attacker access to session cookies, DOM contents, and any actions the victim's session permits.
Refer to the Patchstack Vulnerability Report for additional technical context.
Detection Methods for CVE-2025-30540
Indicators of Compromise
- Unexpected <script>, <iframe>, or event-handler attributes (for example onerror, onload) stored in AvaiBook plugin database tables.
- WordPress audit log entries showing high-privilege accounts editing AvaiBook content shortly before user-reported anomalies.
- Outbound requests from browser sessions to unfamiliar domains after users view AvaiBook-rendered pages.
Detection Strategies
- Query WordPress database tables associated with the AvaiBook plugin for entries containing HTML tags or JavaScript pseudo-protocols such as javascript:.
- Deploy a web application firewall (WAF) rule set that inspects POST parameters targeting AvaiBook endpoints for XSS payload patterns.
- Use Content Security Policy (CSP) violation reports to identify inline scripts executing on pages rendered by the plugin.
Monitoring Recommendations
- Monitor WordPress wp-admin activity for privilege changes and plugin configuration edits by administrator accounts.
- Enable browser telemetry collection to correlate script execution events with page URLs served by the AvaiBook plugin.
- Alert on new outbound domains contacted by admin browser sessions after visiting plugin-controlled pages.
How to Mitigate CVE-2025-30540
Immediate Actions Required
- Deactivate the AvaiBook plugin if a patched version above 1.2 is not yet available for your installation.
- Audit existing AvaiBook content and remove any records containing untrusted HTML or script fragments.
- Rotate credentials and invalidate active sessions for any WordPress users who may have viewed injected pages.
Patch Information
At the time of the NVD entry, the vulnerability affects AvaiBook versions up to and including 1.2. Consult the Patchstack Vulnerability Report for the current fixed version and apply the vendor-supplied update as soon as it is available.
Workarounds
- Restrict plugin administrative capabilities to a minimal set of trusted accounts and enforce multi-factor authentication.
- Implement a strict Content Security Policy that disallows inline scripts and unapproved script sources on WordPress pages.
- Place the site behind a WAF configured with signatures for stored XSS payloads targeting WordPress plugins.
# Example Content Security Policy response header for WordPress
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
