IMO, it's as safe as any broadcast on-line banking - in other words, not safe at all.
If you have a significant amount of money at risk, doing any banking not in person is vulnerable to a greater or lesser extent.
Personally, I will not do any banking via personal computing device of any sort because it is too vulnerable to fraud & hacking.
I also have concluded that anything you place on the web, irrespective of the security, should be considered public information. How many commercial credit card records, medical data, social security, etc datasets have been hacked ? Too many to count.