I'm glad Apple added a feature to identify sneaky URLs that use other scripts to make a URL look like a well-known one.
Here is a sample of a URL containing an imposter letter "a":
http://www.аpple.com/
That is not a Latin-1 letter "a" in the word "apple". Instead, it is a Cyrillic lowercase a and there is a non-Apple website at that URL. The entity used is: & # 1 0 7 2 ;
You might be fooled by this URL before you apply this Security Update but should not be fooled afterwards, because the URL in your Address Bar will show as "www.xn--pple-43d.com/" instead of as "www.apple.com".
You can use the link above, before and after you update, to test how the change works.