In Fiber before version 1.12.6, the filename that is given in c.Attachment() (https://docs.gofiber.io/ctx#attachment) is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc. A possible workaround is to serialize the input before passing it to ctx.Attachment().

Affected: Go: github.com/gofiber/fiber

### Impact The filename that is given in [c.Attachment()](https://docs.gofiber.io/ctx#attachment) is not escaped, and therefore vulnerable for a CRLF injection attack. I.e. an attacker could upload a custom filename and then give the link to the victim. With this filename, the attacker can change the name of the downloaded file, redirect to another site, change the authorization header, etc.

### Steps to reproduce ```go package main

import "github.com/gofiber/fiber"

const badFileName = "another secret document.pdf\"\r\nLocation: google.com\r\nAuthorization: \"example_of_session_fixation"

func splitTheResponse(c *fiber.Ctx) { c.Attachment(badFileName) }

func main() { app := fiber.New() app.Get("/attack", splitTheResponse) app.Listen("127.0.0.1:8080") } ``` ``` HTTP/1.1 200 OK Date: Fri, 10 Jul 2020 19:47:04 GMT Content-Type: application/octet-stream Content-Length: 0 Content-Disposition: attachment; filename="another secret document.pdf" Location: google.com Authorization: "example_of_session_fixation" ```

### Patches This issue has been patched in `v1.12.6` with commit [579](https://github.com/gofiber/fiber/pull/579/commits/f698b5d5066cfe594102ae252cd58a1fe57cf56f) escaping the filename by default.

### Workarounds You could of course serialize the input yourself before passing it to `ctx.Attachment()`, this is actually a good practice by default. But in case you forget, we got you covered 👍

### References A CRLF injection attack is one of several types of inject…