Bottle Jacks can be dangerous just like any other jack can be dangerous.
When using a jack to jack up a car or vehicle makes sure to use jack stands for support of the vehicle whether you use a bottle jack or a floor jack.
Also make sure the jack whether it's a bottle jack or floor jack is on a stable and level surface and not tipping over or prone to tipping over.
When jacking up something with a jack whether it's a bottle jack or floor jack go slowly and if you notice the jack slipping out from underneath the thing you're lifting then stop and slowly lower the jack back down and start over again.
Harbor Freight bottle jacks are good jacks.
I have 6 of the Harbor Freight bottle jacks and they have been working fine for me for 5 years now and I use them quite a bit jacking up cars and even jacked up my house with a couple of the Harbor Freight bottle jacks.
The Harbor Freight bottle jacks are pretty good quality bottle jacks for being Harbor Freight bottle jacks.
You can buy more expensive bottle jacks but if you're an occasional user of the bottle jacks then the Harbor Freight bottle jacks will work just fine for you.
Harbor Freight has some good products even though they sometimes get a bad rep but the tools are cheap and if you pay for cheap tools then you get cheap tools.
But for most people that use a bottle jack or their tools sparingly then Harbor Freight is a good choice for cheap good quality tools.
Higher cost tools are what professionals use but they have to rely on those tools so it's worth paying extra money for good quality built long lasting tools.
But for the homeowner or hobbyist then cheap tools will work just fine.