Callback-url-file-3a-2f-2f-2fhome-2f-2a-2f.aws-2fcredentials «REAL - Checklist»

Do not allow the file:// protocol. Only allow http:// and https:// .

The string callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F.aws-2Fcredentials is a URL‑encoded representation of the following plaintext string:

By providing this string to a parameter that expects a URL (like a webhook or profile picture uploader), an attacker attempts to force the server to "fetch" its own local secret files and return the contents in the application response. callback-url-file-3A-2F-2F-2Fhome-2F-2A-2F.aws-2Fcredentials

If you’re building an application that handles callback URLs, follow this checklist:

: The target path. In Linux systems, /home/user/.aws/credentials is the default location for the AWS Command Line Interface (CLI) and SDKs to store API keys ( aws_access_key_id and aws_secret_access_key ). The * acts as a wildcard, attempting to grab the credentials of any user on the system, regardless of the application's specific username. Why is this Targetted? (The Role of AWS Credentials) Do not allow the file:// protocol

Ensure the web application runs as a restricted user (e.g., www-data or nobody ) rather than root or a user with home directory access, limiting what files can be read even if an SSRF occurs. Conclusion

: A parameter often used in OAuth flows or webhooks where a server is told to send data to a specific location. If you’re building an application that handles callback

Callback URLs, also known as redirect URIs, are URLs that an application or service redirects a user to after a specific action, such as authentication or authorization. These URLs are crucial in implementing secure authentication and authorization flows, especially in OAuth-based systems. When a user attempts to access a protected resource, the application redirects them to an authorization server, which then redirects them back to the application via a predefined callback URL.

Never allow dynamic or unvalidated inputs to dictate redirections or file system lookups.

: The parameter likely used by the application to redirect or fetch data after a process completes.