You’ll want these updates. Apple has released macOS 14.3.1 Sonoma, iOS 17.3.1, and iPadOS 17.3.1 to fix a bug in WebKit that has been causing significant annoyance among Apple users since mid-December 2023 (see “macOS 14.3 Sonoma Text Display Bug to Be Fixed Soon,” 7 February 2024). The day after the other updates, Apple pushed out Safari 17.3.1 to fix the bug in macOS 13 Ventura and macOS 12 Monterey.
The bug caused words or entire lines to seem to disappear and reappear, jump around, or overwrite other text while you were typing in any app that relied on WebKit, most notably Mail, Notes, and Safari, but also including third-party apps like Mimestream and MarsEdit. The problem was disconcerting but primarily cosmetic—the actual text wasn’t changing, although there were reports that submitting a Web form with mangled text could lock it into an undesirable state. Any action that caused the window to be redrawn—resizing, switching to another window and back, closing and reopening—would return the affected text to its correct state, at least temporarily. Although most reports revolved around Mac apps, iOS apps were also affected.
Users and developers alike have been reporting the bug to Apple for some time now, and it was fixed in the open-source WebKit browser engine several weeks ago. There’s no telling why it took Apple so long to deploy these updates, but the company may have been waiting to see if it could include security fixes (there aren’t any) or delay until the next scheduled updates. (One developer told me that the bug was present in macOS 14.4 beta 1 but was fixed in 14.4 beta 2.)
Apple also released watchOS 10.3.1, noting only generic “improvements and bug fixes.” Since watchOS also relies on WebKit, it probably received the update, but Apple didn’t see the need to mention that fact in the release notes, given that text entry on the Apple Watch is uncommon. tvOS has seemingly not received an update, likely because text entry is even less common there, though I expect Apple to integrate the new WebKit version in a future update.