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# Web Cache Deception
> Web Cache Deception (WCD) is a security vulnerability that occurs when a web server or caching proxy misinterprets a client's request for a web resource and subsequently serves a different resource, which may often be more sensitive or private, after caching it.
## Summary
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## Exploit
1. Browser requests a resource such as `http://www.example.com/home.php/non-existent.css`.
2. Server returns the content of `http://www.example.com/home.php`, most probably with HTTP caching headers that instruct to not cache this page.
3. The response goes through the proxy.
4. The proxy identifies that the file has a css extension.
5. Under the cache directory, the proxy creates a directory named home.php, and caches the imposter "CSS" file (non-existent.css) inside.
Example of Web Cache Deception:
Imagine an attacker lures a logged-in victim into accessing `http://www.example.com/home.php/non-existent.css`
1. The victim's browser requests the resource `http://www.example.com/home.php/non-existent.css`
2. The requested resource is searched for in the cache server, but it's not found (resource not in cache).
3. The request is then forwarded to the main server.
4. The main server returns the content of `http://www.example.com/home.php`, most probably with HTTP caching headers that instruct not to cache this page.
5. The response passes through the cache server.
6. The cache server identifies that the file has a CSS extension.
7. Under the cache directory, the cache server creates a directory named home.php and caches the imposter "CSS" file (non-existent.css) inside it.
8. When the attacker requests `http://www.example.com/home.php/non-existent.css`, the request is sent to the cache server, and the cache server returns the cached file with the victim's sensitive `home.php` data.
![WCD Demonstration](Images/wcd.jpg)
### Methodology - Caching Sensitive Data
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5. The content of the cache is displayed
Video of the attack by Omer Gil - Web Cache Deception Attack in PayPal Home Page
[![DEMO](https://i.vimeocdn.com/video/674856618.jpg)](https://vimeo.com/249130093)
[![DEMO](https://i.vimeocdn.com/video/674856618-f9bac811a4c7bcf635c4eff51f68a50e3d5532ca5cade3db784c6d178b94d09a-d)](https://vimeo.com/249130093)
**Example 2** - Web Cache Deception on OpenAI
1. Attacker crafts a dedicated .css path of the `/api/auth/session` endpoint.
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| CLASS | EXE | JS | PICT | SWF | XLS | XLSX |
## Labs
* [PortSwigger Labs for Web cache deception](https://portswigger.net/web-security/all-labs#web-cache-poisoning)