FileBrowser Quantum is a free, self-hosted, web-based file manager. Prior to version 1.4.3-beta, the `subtitlesHandler` endpoint (`GET /api/media/subtitles`) accepts two user-controlled query parameters: `path` and `name`, both of which are used in filesystem operations without sanitization, creating two independent path traversal vectors. The primary vector is the `path` parameter: it is passed directly to `idx.GetRealPath()` without calling `SanitizeUserPath()`, allowing an attacker to escape the storage root and set `parentDir` to any directory on the host. No existing anchor file is required. The secondary vector is the `name` parameter: it is joined with `parentDir` via `filepath.Join(parentDir, name)` without stripping directory components, allowing traversal relative to any resolved `parentDir`. Any authenticated user (regardless of role or permissions) can exploit either vector to read any text file readable by the server process, including `/etc/passwd`, SSH keys, database credentials, and JWT signing keys. Version 1.4.3-beta patches the issue.

Affected: Go: github.com/gtsteffaniak/filebrowser/backend

### Summary

The `subtitlesHandler` endpoint (`GET /api/media/subtitles`) accepts two user-controlled query parameters: `path` and `name`, both of which are used in filesystem operations without sanitization, creating two independent path traversal vectors.

The primary vector is the `path` parameter: it is passed directly to `idx.GetRealPath()` without calling `SanitizeUserPath()`, allowing an attacker to escape the storage root and set `parentDir` to any directory on the host. No existing anchor file is required.

The secondary vector is the `name` parameter: it is joined with `parentDir` via `filepath.Join(parentDir, name)` without stripping directory components, allowing traversal relative to any resolved `parentDir`.

Any authenticated user (regardless of role or permissions) can exploit either vector to read any text file readable by the server process, including `/etc/passwd`, SSH keys, database credentials, and JWT signing keys.

### Details

**1. `path` parameter lacks `SanitizeUserPath()` — primary vector (`http/media.go:54`)**

```go userscope, err := d.user.GetScopeForSourceName(source) // ... realPath, _, err := idx.GetRealPath(userscope, path) // path is raw user input, no sanitization // ... parentDir := filepath.Dir(realPath) // line 59: attacker controls this directory ```

`SanitizeUserPath()` explicitly rejects `..` segments:

```go func SanitizeUserPath(userPath string) (string, error) { // ... for _, segment := range segments { if segm…