Applications that pass attacker-controlled URLs to `webpage` versions before
2.1.0 may be vulnerable to server-side request forgery (SSRF) or local file
disclosure.
`HTTP::fetch` and `Webpage::from_url` passed URLs to libcurl without
restricting the URL scheme or validating the resolved destination IP address.
Redirects were followed without checking whether the new destination was
internal. Depending on how the application uses the response, an attacker
could:
- Read local files accessible to the application process using `file://` URLs.
- Cause requests to internal or link-local services (e.g. cloud metadata
endpoints at `http://169.254.169.254`) via direct private-IP URLs or by
chaining HTTP redirects through an attacker-controlled server.
Starting in 2.1.0, `HTTP::fetch` and `Webpage::from_url` reject non-HTTP(S)
URL schemes and destinations that resolve to non-public IP addresses, including
after redirects. Applications that intentionally fetch trusted internal
resources can opt in to the previous behavior with `HTTP::fetch_unrestricted`
or `Webpage::from_url_unrestricted`.
Reported by [Aiden Mohan](https://github.com/AidenMohan).