Takes a second or so to load on mine (iOS Safari). But then it shows correctly, even if the second diagram is a bit small (it fits in a quarter of the 1in circle).
Well iOS Safari is in general buggy and tends to display the "a problem repeatedly occurred" message on many other slightly heavy web pages. This web page shouldn't be blamed for causing Safari to crash.
By definition buggy websites that crash the browser are bugs in the browser.
It may have security implications, or it may not. It might just be an innocent case of someone using assertions instead of proper error reporting. Nevertheless it's a bug in the browser.