Thats general for all cameras. The main difference between brands is better support and updates. I don't own a Xiomi camera, but do own quite a few Foscam ones. Generally software bugs and firmware updates will be released more regularly for more well known brands like Foscam.
Is that in general for all cameras or just well received brands? (I was originally looking at the Xiomi one which looked quite low profile)
Choose a strong password and keep the firmware up to date and you'll be fine.
How is the security of attacks from the internet? I've been reading about these cheap ones and they even have built in vulnerabilities...