: This is a URI scheme that instructs a system to read a file from the local file system rather than a website.

: The %2F (encoded as -2F in some specific application filters) represents a forward slash. The ../ sequence is a "step up" in the directory tree. Using multiple sequences (e.g., ../../../../ ) allows the attacker to reach the root directory ( / ) from a nested web folder.

Given the decoded path, it's likely that this is an attempt to access a sensitive file:

If the application doesn't properly sanitize the input, an attacker can swap user123.jpg with the malicious string. The server, thinking it is still performing a legitimate task, navigates through its own file system, finds the AWS credentials file, and displays its contents (the Access Key ID and Secret Access Key) directly in the attacker's browser. The Impact: Complete Cloud Takeover

That’s why credentials is a crown jewel for attackers.