X....... reports that a Stealth Screen has been discovered around the planet! Cloaking has increased by 30%
Planet last attacked 6 months 2 week ago.

This message did welcome me today just after opening the game. Is it common to have planet with additional effect during owning the planet?

Just to know, whether it can happen to me again

If by common you mean maybe once a year or so, then yes it is common. (maybe every 6 mos if you're governor)

As to if it will happen to you again - yes, in about a year or so.

What else is on it?

nothing else, so far there were only temporary planet events.

I got the same thing about a month ago, it's just random. But if it's on a big enough planet will make a good storage tower planet for yourself, or sell it to some else to use!!