WordPress Scoutnet Kalender 1.1.0 Cross Site Scripting

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Advisory ID: SYSS-2019-045   
Product: "Scoutnet Kalender" for WordPress  
Manufacturer: Scoutnet and Björn Stromberg  
Affected Version(s): 1.1.0  
Tested Version(s): 1.1.0  
Vulnerability Type: Cross-Site Scripting (CWE-79)   
Risk Level: Medium  
Solution Status: Open  
Manufacturer Notification: 2019-10-23  
Solution Date: -  
Public Disclosure: 2019-12-09  
CVE Reference: CVE-2019-19198  
Author of Advisory: Simon Moser, SySS GmbH  
  
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Overview:  
  
"Scoutnet Kalender" is a plug-in for WordPress to display one oder many  
Scoutnet calendars as a widget, on a page or an article.  
  
Due to a missing input sanitation, it is vulnerable to cross-site scripting.  
  
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Vulnerability Details:  
  
The plug-in allows to include calendars from Scoutnet into WordPress websites.  
Calendars are not only included by websites administrated by the same person  
as the calendar but also by other sites. When events from a calendar are  
included, the data is not being sanitized. This allows an attacker with control  
over an embedded calendar to inject scripts into the attacked site.  
  
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Proof of Concept (PoC):  
  
1. Create an event with the following value of the "Info" field:  
<script>alert("Cross-Site Scripting");</script>  
  
2. Save the event  
  
3. Visit the page where the calendar is embedded  
  
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Solution:  
  
As long as the default template is not changed by the manufacturer, SySS GmbH  
recommends to change the provided template to sanitize fields controlled by  
other users. If this is not possible because interactive content needs to be  
included, the set of users with permissions to create and change events should  
be as small as possible.  
  
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Disclosure Timeline:  
  
2019-10-20: Vulnerability discovered  
2019-10-23: Vulnerability reported to manufacturer  
2019-11-12: Discussion with the manufacturer about security by design  
2019-12-09: Public disclosure of vulnerability  
  
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References:  
  
[1] Product website for "Scoutnet Kalender"  
https://de.wordpress.org/plugins/scoutnet-kalender/  
[2] SySS Security Advisory SYSS-2019-045  
https://www.syss.de/fileadmin/dokumente/Publikationen/Advisories/SYSS-2019-045.txt  
[3] SySS Responsible Disclosure Policy  
https://www.syss.de/en/news/responsible-disclosure-policy/  
  
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Credits:  
  
This security vulnerability was found by Simon Moser of SySS  
GmbH.  
  
E-Mail: [email protected]  
Public Key: https://www.syss.de/fileadmin/dokumente/PGPKeys/Simon_Moser.asc  
Key ID: 0x5FF2CFC6  
Key Fingerprint: E3C2 A86E 530D 8BD3 C40B 6542 8376 5B89 5FF2 CFC6   
  
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Disclaimer:  
  
The information provided in this security advisory is provided "as is"   
and without warranty of any kind. Details of this security advisory may  
be updated in order to provide as accurate information as possible. The  
latest version of this security advisory is available on the SySS Web  
site.  
  
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Copyright:  
  
Creative Commons - Attribution (by) - Version 3.0  
URL: http://creativecommons.org/licenses/by/3.0/deed.en  
  
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