Erratic display after confirmation

Hello,

I experienced an erratic behaviour after test-subscribing.

Everything went fine, I clicked on the mail to confirm the subscription and the page with the confirmation message (which I translated into German, also happend with the original English text) appeared.

Apperead it did, everywhere. In the footer, in the side bar all menu entries have been replaced by the confirmation message (see screenshot).

Screenshot

How may I get rid of that? Thanks in advance.

https://www.ads-software.com/plugins/subscribe2/