K2 Smartforms 4.6.11 Server-Side Request Forgery

`# Vulnerability type: Server Side Request Forgery  
# Vendor: https://www.k2.com/  
# Product: K2 Smartforms  
# Affected version: 4.6.11  
# Credit: Foo Jong Meng  
# CVE ID: CVE-2018-9920  
  
# DESCRIPTION:  
  
Server side request forgery exists in the runtime application in K2 smartforms 4.6.11 via a modified hostname in an https://*/Identity/STS/Forms/Scripts URL.  
  
By replacing the "GET" parameter to any external domain (i.e. https://www.external-domain.com) while accessing the affected application (e.g.  
https://url/Identity/STS/Forms/Scripts).   
  
The resulting page shows URL with https://url/Identity/STS/Forms/Scripts but rendering https://www.external-domain.com in the body (aka local web defacement).   
  
A port scan on the internal servers can be performed by changing the "GET" parameter URL and analysing the results of the return page.  
  
  
# PROOF OF CONCEPT:  
1. Use a web proxy (i.e zapproxy, burp) to intercept "GET" request for:  
https://url/Identity/STS/Forms/Scripts  
  
2. Replace the "GET" parameter to any external domain (i.e. https://www.external-domain.com/)  
  
3. The resulting page is one with https://url/Identity/STS/Forms/Scripts but showing https://www.external-domain.com/ in the body.  
`