Cross-Site Request Forgery (CSRF) in firefly-iii/firefly-iii
Reported on
Aug 20th 2021
✍️ Description
Attacker able to set default currency with CSRF attack.
It does not matter at all that your application run in localhost or elsewhere, just it is enough to run on a browser and another low privilege user or attackers know the IP address or hostname of your application.
In CSRF attacks it is necessary that a user logged into your application and just going to a malicious website and after that only with a redirection attacker can perform attack on unprotected endpoint, this means only with visiting a site a unwanted action will be perform without that user aware from that.
🕵️♂️ Proof of Concept
1.fisrt admin already should be logged in Browser.
2.Open the PoC.html (it is auto-submit).
3.Here a set default currency with id 22 will be set to default after the PoC.html file opened.
// PoC.html
<html>
<body>
<script>history.pushState('', '', '/')</script>
<form action="https://demo.firefly-iii.org/currencies/default/22">
<input type="submit" value="Submit request" />
</form>
<script>
document.forms[0].submit();
</script>
</body>
</html>
This PoC can perform attack without that users noticed and Also PoC can send multiple request at same time that means attacker can Bruteforce all possible actions ( with using multiple Iframe )
💥 Impact
This vulnerability is capable of change default currency.
Fix
The easiest way that you set strict attribute on each cookie, Or you set Lax and Use GET requests only for receiving data not changing them.
The best way is that you set a CSRF token in each endpoint.
Occurrences
Nice, also fixed. Should also be up on the demo site. Fix will be part of the normal release cycle.
CVE published! It should be made publically available via MITRE/NVD shortly.