> 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/csrf/samesite-strict-bypass-via-client-side-redirect.md).
# SameSite Strict Bypass via Client-Side Redirect
SameSite Strict Bypass via Client-Side Redirect notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### SameSite Strict Bypass via Client-side Redirect
The change email form of the lab is vulnerable to the CSRF. The aim is to change the victim's email address by hosting the exploit on the supplied exploit server.
**Test access**/ Account used in the lab: `wiener:peter`
### Observations Principales
1. The e-mail change feature works via a GET request of this type:
```
/my-account/change-email?email=test@test.com&submit=1
```
By sending a JavaScript redirect like this:
```javascript
```
* the page asks to authenticate if the user is not logged in — the query does not take the session cookie when it comes from another site.
The `Set-Cookie` header contains `SameSite=Strict`, which prevents the sending of the session cookie when browsing initiated from another context (cross-site), normally blocking classic redirection attacks.
### Area Exploited (comments → Confirmation → Redirection)
1. There is a comment area that then redirects to:
```
post/comment/confirmation?postId=8
```
A script on the confirmation page extracts the `postId` parameter and redirects after 3 seconds to the corresponding post:
```javascript
redirectOnConfirmation = (blogPath) => {
setTimeout(() => {
const url = new URL(window.location);
const postId = url.searchParams.get("postId");
window.location = blogPath + '/' + postId;
}, 3000);
}
```
```javascript
window.location = blogPath + '/' + postId;
```
```
window.location = blogPath + '/' + ../my-account;
```
Observing this behavior, we note that `postId` is not strictly obliged: if one changes its value (e.g. `test`), the redirection is to `.../test` without apparent validation.
#### Surrounding the SameSite Strict via Manipulated Path
Idea: Replace redirection to `blogPath + '/' + postId` with `postId` containing relative `..` segments to reach a path from the target site (back-directory), for example:
`/post/comment/confirmation?postId=../my-account`
* the redirect then leads to a higher directory without blocking the session cookie.
By building a more specific `postId`, we directly target the change function of the email:
```
/post/comment/confirmation?postId=../../my-account/change-email?email=hack@jordann.com%26submit=1
```
Simple redirect to the e-mail change page:
```javascript
```
---
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