Zabbix 5.0.0 - Stored XSS via URL Widget Iframe

# Exploit Title: Zabbix 5.0.0 - Stored XSS via URL Widget Iframe
# Date: 8/11/2020
# Exploit Author: Shwetabh Vishnoi
# Vendor Homepage: https://www.zabbix.com/
# Software Link: https://www.zabbix.com/download
# Affected Version: Zabbix before 3.0.32rc1, 4.x before 4.0.22rc1, 4.1.x through 4.4.x before 4.4.10rc1, and 5.x before 5.0.2rc1
# CVE : CVE-2020-15803

Affected URL/endpoint(s):
http://192.168.1.7/zabbix.php?sid=f7ca8c8270ce38c7&action=dashboard.widget.check

Affected Param: <iframe src="http://localhost/hello.html" scrolling="auto"
id="iframe" class="widget-url" width="100%" height="100%"></iframe>

Description: The application contains a widget functionality within Global
View Dashboard which can be used by a malicious admin to propagate stored
cross site scripting attack. The “URL” widget iframe does not have any
inbuilt restrictions for the content executing within.

Impact: The malicious webpages within iframes can be used for hosting forms
for Phishing, malware propagation, forced redirections etc.

The affected Global View dashboard is displayed to all the users of the
application, so all the users will be affected with this vulnerability.

Reproduction Steps:
1. Login to the application with Admin
2. In Global View Dashboard, Add a widget
3. Select Type – “URL”, fill any random values for Name, Refresh Interval.
4. Now, in the URL parameter, enter a malicious URL.
5. For demo purpose, I have hosted a web server on my machine and hosted a webpage http://localhost/hello.html. (Alternatively, you can use “ http://14.rs” to display popups.)
6. The malicious webpage containing payload will be executed on the dashboard via iFrame.
7. The executed content can redirect the user to a malicious page (We have used Bing page for redirection).