iOS 16.5.1 (a) and macOS 13.4.1 (a) were rolled out by Apple on Monday as Rapid Security Response (RSR) updates for the company’s phones, tablets, and Mac computers. The update included fixes for a vulnerability in Apple’s browser engine that may have been used by hackers to execute malicious code remotely on a user’s device and gain access to their data. However, hours after rolling out the security update, Apple has reportedly pulled the software update due to a bug and is expected to roll it out once the issue is resolved.

The iOS 16.5.1 (a) and iPadOS 16.5.1 RSR updates were rolled out to users on Monday, along with a fix for a WebKit vulnerability that would allow arbitrary code execution while processing malicious web content. Apple advised all users to install the update as it was aware of a report that the security flaw was actively exploited and credited an anonymous researcher with identifying the flaw.

However, user reports on the MacRumors forum claimed that websites like Facebook, Instagram, Zoom, and WhatsApp began to show them a warning that the company’s Safari browser wasn’t supported. This is reportedly due to the inclusion of the (a) from update version in the “user agent” for Safari, that identifies the user when connecting to a website.

Apple has reportedly pulled the update after the bug was discovered. Users who have downloaded and installed the update can downgrade to iOS 16.5.1 and iPadOS 16.5.1 by visiting Settings > General > About > iOS Version and tap on Remove Security Update.

Gadgets 360 was able to confirm that the RSR update was no longer available to download after downgrading to iOS 16.5.1 (20F75). Apple is expected to release an update for iOS, iPad, and macOS once the bug related to the Safari user agent has been resolved, and users who have downgraded due to the issue should install the update when it is released again with fixes for the security flaws.