Apple launched yesterday an urgent security update that has had to be withdrawn as urgently because it caused failures in websites and applications, and promises a solution shortly.
iOS 16.5.1 (and the corresponding version of iPadOS) was released yesterday. It was specifically the iOS 16.5.1(a) version that came in the form of the recently released “Quick security updates”. These are small quick updates so they don't take long to download and once installed on our device they have the peculiarity that they can be uninstalled. This update fixed a serious security flaw in Safari, so its installation was more than recommended, but shortly after it disappeared from their servers, and those who had not installed it immediately could no longer do so because the option did not even appear in their device settings.
And it is that this security update solved that security flaw but It caused some websites and applications to not work correctly, due to changes made to Safari. Apple itself has recognized the failure and promises a solution shortly.
Apple is aware of an issue where this Express Security Update could prevent some websites from displaying correctly. Rapid Security Response iOS 16.5.1(b) and iPadOS 16.5.1(b) will be available soon to fix this issue.
What to do if you installed the update? It may be the case that you do not notice anything and everything works correctly for you. Some of the websites that did not work with this version are Facebook and Instagram, so if you don't usually visit them, you may not have even realized that the problem exists. In such a case, all you can do is wait for the new update and that's it. But if you are noticing these problems on some websites and apps, you can uninstall yesterday's update very easily. To do this, you must access the settings of your iPhone or iPad, and within the section "General> Information> iOS version" you will see the option to uninstall this security update. Do not panic.