With this addon you can secure your css cookies, granted you've fully migrated your site to https.
So now you are thinking is this really necessary, well yes and I could explain it all right here but this article really says it all.
As a bonus, we made this adon compatible all the way back to 4.2.x till the latest.
Side note: this won't work when you use a proxy ssl like cloudflare.
Download the module and install it, and you're done.