Problem:
When a user navigates directly to a URL (no HTTP_REFERER) and this user has no abilities to view this page (see the example code below), redirect()->back() redirects to the same page, causing an infinite loop.

Example of redirect back in the controller:

if (auth()->user()->cannot('viewAny', Example::class)) {
    return redirect()->back()->with('status', 'You are not authorized!')
}

The $fallback parameter only triggers when HTTP_REFERER is completely absent, but not when it equals the current URL.

Proposed solution:
Modify Redirector::back() to also compare previous URL with current URL, and use a configurable fallback URL:

1. Add fallback_url to config/app.php and FALLBACK_URL parameter to .env file:

'fallback_url' => env('FALLBACK_URL', '/'),

2. Modify Redirector::back():

public function back($status = 302, $headers = [], $fallback = null)
{
    $previous = $this->generator->previous();
    $current  = $this->generator->current();

    $url = ($previous && $previous !== $current)
        ? $previous
        : $fallback ?? config('app.fallback_url', '/');

    return $this->createRedirect($url, $status, $headers);
}