Information
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Advisory by Netsparker
Name: XSS Vulnerability in MailPoet Newsletters
Affected Software : MailPoet Newsletters
Affected Versions: v2.6.19 and possibly below
Vendor Homepage : http://www.mailpoet.com/
Vulnerability Type : Cross-site Scripting
Severity : Important
CVE-ID : TBA
Status : Fixed
Netsparker Advisory Reference : NS-16-002

Description
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By exploiting a Cross-site scripting vulnerability the attacker can
hijack a logged in user’s session. This means that the malicious
hacker can change the logged in user’s password and invalidate the
session of the victim while the hacker maintains access. As seen from
the XSS example in this article, if a web application is vulnerable to
cross-site scripting and the administrator’s session is hijacked, the
malicious hacker exploiting the vulnerability will have full admin
privileges on that web application.

Technical Details
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Proof of Concept URL for XSS in MailPoet Newsletters v2.6.19:

wordpress-4.4.1/?wysija-page=1&controller=confirm&wysija-key='"--></style></scRipt><scRipt>alert(0x0034B4)</scRipt>&action=unsubscribe&demo=1&wysijap=subscriptions

For more information on cross-site scripting vulnerabilities read the
following article:
https://www.netsparker.com/web-vulnerability-scanner/vulnerability-security-checks-index/cross-site-scripting-xss/

Advisory Timeline
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18 Jan 2016 - First Contact
29 Jan 2016 - Vendor Fixed
02 Feb 2016 - Advisory Released

Solution
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Patch released by MailPoet and annocunced here:
https://wordpress.org/plugins/wysija-newsletters/changelog/. Download
the latest version.

Credits & Authors
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These issues have been discovered by Omar Kurt while testing
Netsparker Web Application Security Scanner -
https://www.netsparker.com/web-vulnerability-scanner/.

About Netsparker
--------------------
Netsparker web application security scanners find and report security
flaws and vulnerabilities such as SQL Injection and Cross-site
Scripting (XSS) in all websites and web applications, regardless of
the platform and technology they are built on. Netsparker scanning
engine’s unique detection and exploitation techniques allow it to be
dead accurate in reporting vulnerabilities. The Netsparker web
application security scanner is available in two editions; Netsparker
Desktop and Netsparker Cloud. Visit our website
https://www.netsparker.com for more information.

Onur Yılmaz - National General Manager

Netsparker Web Application Security Scanner
T: +90 (0)554 873 0482