> 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/xss/reflected-xss-protected-by-strict-csp-with-dangling-markup.md).
# Reflected XSS Protected by a Very Strict CSP Attack by Dangling Markup
Reflected XSS Protected by a Very Strict CSP Attack by Dangling Markup notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and rem
### Reflected XSS Protected by Very Strict CSP, with Dangling Markup Attack
#### Lab Objective
* Conduct an XSS attack that bypasses the CSP and exfils the CSRF token of a simulated user (via Burp Collaborator).
* Then use this token to change the victim's email address to `hacker@evil-user.net`.
* The vector visible to the victim must contain the word **Click** (e.g. `Click me`) to encourage it to click.
* Test account: `wiener:peter`.
#### Observations Initiales
* In the e-mail update form, adding `?email=` to the URL controls the value (`value`) of `email` input.
The field is vulnerable to an injection of HTML tags (examples of testing):
* `test">
test
` → `
` is injected and returned.
```html
test">
test
```
* `test">` → `
```
The browser console indicates a security policy block:
{% hint style="danger" %}
Content-Security-Policy: The page's settings blocked an inline script (script-src-elem) from being executed because it violates the following directive: “script-src 'self'”
{% endhint %}
Observed CSP header:
`content-security-policy`/ `default-src 'self';object-src 'none'; style-src 'self'; script-src 'self'; img-src 'self'; base-uri 'none';`
#### Attack Strategy (dangling Markup)
* Instead of injecting a `
```
* Once the victim is redirected and the button clicked, the CSRF token is found in the logs of the exploit server.
#### Post-exfiltration Operation: Use of CSRF Token to Change Email
* After obtaining the CSRF token (from the logs of the exploit server), an HTML page is built that submits a POST to `/my-account/change-email` with:
* `email = hacker@evil-user.net`
* `CSRF = `
Example of HTML PoC generated (by Burp or manually) to perform automated POST query
```html
```
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.
Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:
```
GET https://hacking-notes.jord4n.pro/web/xss/reflected-xss-protected-by-strict-csp-with-dangling-markup.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)
.png?alt=media)