Nginx updated itself and broke everything, how?

Question

Nginx

Greetings! Tonight, I automatically updated nginx myself to a newer version from the dotdeb repository (once I added it to install fresh versions of php). So tonight a new version of nginx 1.8 was released in this repository and for some reason it took it and installed itself, how so? And how can I turn this off? As a result, the site did not work for 7 hours.
Ispmanager 5 panel on the server, maybe she did it?
Debian 7
isp 5

Answer 1

for some reason I took it and installed it myself, how so?

Itself in niksa nothing happens. This means that automatic updates and installation of new versions of packages are configured. Remove if you don't like it.
And third party repos too, if the qualifications are not sufficient to use them.

Answer 2

Nothing happens unless configured.
last -n 10
tail -n 100 /var/log/apt/history.log
See what else is in /etc/nginx, there may be an old nginx.conf file