MailPoet Newsletters 2.6.19 Cross Site Scripting

`Information  
--------------------  
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  
--------------------  
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  
--------------------  
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  
--------------------  
18 Jan 2016 - First Contact  
29 Jan 2016 - Vendor Fixed  
02 Feb 2016 - Advisory Released  
  
Solution  
--------------------  
Patch released by MailPoet and annocunced here:  
https://wordpress.org/plugins/wysija-newsletters/changelog/. Download  
the latest version.  
  
Credits & Authors  
--------------------  
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  
`