When playing around with my blog I discovered that is possible to temporary disable the blogger.com toolbar just adding a new parameter to the URL.
This is not a security issue and should not be considered a threat to any user or blog.
Think of it like a easter egg :-)
It's quite simple to replicate.
... to the URL of any blogger account (works also with a domain associated to blogger) will disable Google Plus buttons and the toolbar.
Google reported that will fix this issue as soon as possible.