This specific string, fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig , is a high-risk security payload typically used to test for vulnerabilities. If a web application is vulnerable, an attacker can use this string to trick the server into reading its own internal configuration files—in this case, the AWS root user's CLI configuration.
Given the breakdown of the URL, we can speculate about its possible use cases: fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig
Never allow users to submit full URLs or file paths directly. Use a Whitelist: fetch-url-file-3A-2F-2F-2Froot-2F.aws-2Fconfig