> For the complete documentation index, see [llms.txt](https://ganesha-hk.gitbook.io/cybersecurity-writeups/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ganesha-hk.gitbook.io/cybersecurity-writeups/port-swigger-ssti-labs/lab-3.md).

# lab-3

## Server-Side Template Injection Using Documentation

**Difficulty:** Practitioner

### Lab Description

This lab is vulnerable to server-side template injection. The template engine is unknown up front.

**Objective:** Identify the template engine, use its documentation to work out how to execute arbitrary code, then delete the `morale.txt` file from Carlos's home directory.

**Credentials:** `content-manager:C0nt3ntM4n4g3r`

### Solution

**Step 1 — Reconnaissance**

There's no information about which template engine the backend uses, so the first task is finding a vulnerable parameter. The lab provides a `content-manager` account — log in with it. Each product page displays a line like:

```
Hurry! Only ... left of Potato Theater at $....
```

This dynamically generated text is a good candidate for injection.

**Step 2 — Locate the editable template**

After logging in, there's no visible email set on the account. Updating the email unlocks the ability to edit/update the page template for each product. Opening the template editor reveals:

```html
<p>Hurry! Only ${product.stock} left of ${product.name} at ${product.price}.</p>
```

The `${...}` syntax is characteristic of a **Java-based** template engine.

**Step 3 — Fingerprint the exact engine**

Testing:

```
${ctx.getVariableNames()}
```

triggers an error that gives two useful pieces of information: it confirms the engine is **Apache FreeMarker**, and it reveals that `ctx` isn't a valid object within FreeMarker's default data model.

**Step 4 — Exploit to delete the file**

With FreeMarker confirmed, use its documented `Execute` utility class to run an OS command:

```freemarker
${"freemarker.template.utility.Execute"?new()("rm /home/carlos/morale.txt")}
```

Save/submit this as the product template to trigger execution and delete the file.

### Conclusion

With no engine specified, careful fingerprinting — using syntax artifacts and induced error messages — was enough to identify Apache FreeMarker and reach its documented code-execution utility class.


---

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