Latest update

What security update are you asking about? Specific iOS version?

If you specifically mean today’s 13.5.1 it fixes a potential vulnerability. It would be foolish of Apple to describe it in any detail, because that would become a recipe for hackers to attack iOS devices that have not been updated. Most likely it is a vulnerability that either Apple found or a security researcher discovered and reported to Apple, before hackers discovered it. Typically vulnerabilities that have been made public will be described by Apple, but not ones that have not been seen “in the wild”. I did see a note that Apple just paid a bounty of $100K to an Indian security researcher who reported a vulnerability. This might be the fix for that.

Apple typically does not issue a succinct description of what security updates are about. That is true this time as well.

Security is enhanced as a result of applying this update.

Apple security updates - Apple Support