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- Title: Ninja Forms WordPress Plugin Multiple Cross-Site Scripting Vulnerability
- Vulnerable Version: 2.8.8 and probably prior
 -Tested Version:2.8.8
 - Vendor Notification: 20 November 2014
 - Vendor Patch: 20 November 2014
 -Vulnerability Type: Cross-Site Scripting [CWE-79]
 -CVE Reference: TBC
- Discovered by: Sergio Navarro of Dionach
- - ============================================================

VULNERABILITY
Two XSS vulnerabilities have been discovered in Ninja Forms WordPress plugin which can be exploited against administrators of WordPress (with the vulnerable plugin) to perform Cross-Site Scripting
1)  Reflected XSS
The issue was found in the success notification message that the Ninja Forms plugin displays in users’ browser after users submit their details successfully through the plugin contact form. Anonymous attackers could use the vulnerability to take control of the victim’s browser or steal other users' sessions and so access their personal details.
Proof of concept:
POST http://www.example.com/wp-admin/admin-ajax.php?action=ninja_forms_ajax_submit 
[…]
ninja_forms_field_1=<b onmouseover=alert('XSS!')>TEST</b>
[…]

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2)Stored XSS
This issue was exploited when administrator users with access to the Ninja Forms submissions list attempt to edit the user submitted values. A malicious administration can hijack other users’ session, take control of another administrator’s browser or install malware on their computer.
Proof of concept:
POST http://www.example.com/wp-admin/post.php 
fields[1]=<b+onmouseover=alert('XSS!')>TEST</b> 
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SOLUTION:
Update to Ninja Forms 2.8.11 which includes a fix for this vulnerability 
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Credits: Sergio Navarro of Dionach