CVE-2025-3514 – SureForms – Stored XSS to JS Backdoor Creation – POC

SureForms is a powerful and widely adopted WordPress plugin used for creating customizable forms. With over 200,000 active installations, it is trusted by site administrators for building contact, feedback, and survey forms with ease. However, during a recent plugin assessment, a critical vulnerability was uncovered — a Stored Cross-Site Scripting (XSS) flaw — which allows malicious JavaScript injection through form field attributes. This vulnerability can be exploited by an editor to trigger a JavaScript backdoor, potentially leading to full administrative compromise.

CVE	CVE-2025-3514
	SureForms < 1.4.4
Critical	High
All Time	742 732
Active installations	200 000+
Publicly Published	May 30, 2025
Last Updated	May 30, 2025
Researcher	Dmitrii Ignatyev
OWASP TOP-10	A7: Cross-Site Scripting (XSS)
PoC	Yes
Exploit	No
Reference	https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-3514 https://wpscan.com/vulnerability/fc3da503-a973-44d8-82d0-13539501f8c0/
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Timeline

Discovery of the Vulnerability

The vulnerability was found in the “Default Value” parameter of the Email input block in the form editor. Specifically, when a malicious string containing HTML event handlers (such as onmouseover) was entered into this field, it was stored without sanitization and rendered back to the form editor or users without escaping. As a result, scripts could execute when an admin or user interacts with the form, such as by hovering over the Email field.

Understanding of XSS attack’s

Cross-Site Scripting (XSS) in WordPress often stems from plugin developers trusting user-supplied input and outputting it directly into the DOM without proper escaping. While WordPress includes core functions for sanitization and output escaping, these are not always properly used in third-party plugins. In this case, the default value field in SureForms allowed editors to insert HTML attributes that were later rendered in the admin panel or public site forms. For example, the payload 123" onmouseover=alert(1)// effectively closes the attribute and injects malicious behavior. Similar flaws have historically been used to steal cookies, perform privilege escalation, or inject persistent scripts into admin pages.

Exploiting the XSS Vulnerability

To exploit CVE-2025-3513, an attacker with editor+ privileges:

POC:

1) Create a new Blank Form
2) Put here Email block and change "Default value" field to 123" onmouseover=alert(1)//
3) To trigger XSS you should save this form and reload page. Hover on email block
(Admins and editors are allowed to use JS in posts/pages/comments/etc, so the unfiltered_html capability should be disallowed when testing for Stored XSS using such roles)

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The most severe risk associated with this vulnerability is the creation of a JavaScript backdoor, which allows persistent access and manipulation of the site’s administrative interface. An attacker with editor privileges could prepare a malicious form, wait for an administrator to preview or edit it, and execute arbitrary JavaScript in their session. This script could silently create a new admin account, redirect to phishing pages, or even inject code into theme files via the file editor. On high-traffic or enterprise websites, the damage from such exploitation includes data leaks, unauthorized access, SEO poisoning, or even ransomware drops.

Recommendations for Improved Security

To mitigate this issue and prevent similar vulnerabilities:

• The plugin developer must implement strict input validation and output escaping using WordPress’s esc_attr() or esc_html() functions wherever user data is used in the frontend or backend.
• Users should avoid granting editor roles to untrusted users, especially when plugins allow content customization that renders in sensitive contexts.
• Disable the unfiltered_html capability for roles that do not require it.
• Employ a Web Application Firewall (WAF) that can sanitize user input or block malicious JavaScript patterns.
• Use vulnerability scanners such as WPScan or Wordfence to detect and alert on known plugin vulnerabilities.
• Keep all plugins updated regularly and subscribe to vulnerability feeds.

To prevent this type of attacks vendor used our methods of prevention.

By taking proactive measures to address Stored XSS vulnerabilities like CVE-2025-3514, WordPress website owners can enhance their security posture and safeguard against potential exploitation. Stay vigilant, stay secure.

#WordPressSecurity #StoredXSS #WebsiteSafety #StayProtected #HighVulnerability

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Dmitrii I.