Where is Firebug's Cookies panel gone?

Firebug doesn't show me the Cookies panel anymore. Somebody knows why?

Solution

You got automatically switched to the Firefox DevTools (with Firebug theme), because Firebug is discontinued and doesn't work anymore in multi-process Firefox. See the related Mozilla Hacks blog post for more info.

The equivalent to the Cookies panel in Firebug is the Storage Inspector, which not only allows you to inspect cookies but also the local and session storage, the cache and IndexedDB entries.

This tool needs to be enabled via the settings, though.

This and other things are mentioned in the migration guide for Firebug users.