The core of this keyword lies in the alphanumeric sequence following "file-". In web communication, certain characters are reserved for specific functions. To use these characters as plain text, they must be converted into a % followed by their hexadecimal value. : This is the hex code for a colon ( : ). 2F : This is the hex code for a forward slash ( / ).
: Some environments, such as Node.js or specialized fetch wrappers , use this naming convention to enable or log the ability to "fetch" local files as if they were network resources.
If you’ve stumbled upon the strange-looking string fetch-url-file-3A-2F-2F-2F in developer forums, error logs, or URL encoding tables, you’re not alone. At first glance, it looks like a random sequence of characters. But once you URL-decode it, the meaning becomes clear:
The triple slash /// after a custom scheme is rare, but some systems interpret scheme:///path as an absolute path on the current host. Combined with fetch-url-file , an attacker could try to read local files if the scheme handler naively fetches from the filesystem.
: Use Online String Tools to decode or encode your payloads to bypass simple text-based filters.
(decoded from your string) are often scrutinized by security filters because they can be used in Server-Side Request Forgery (SSRF) attacks to read sensitive local files. Functionality