Apple Closes iOS 18.6 Signing to Block Downgrades

Apple has stopped signing iOS 18.6, blocking downgrades from newer updates due to security issues patched in newer versions. iOS 18.6 was released on July 29 with bug fixes, security improvements, and a fix for a performance issue with the Photos app's Memories feature. The update also included a change to how third-party app marketplaces are handled in the EU. Apple released iOS 18.6.1 and iOS 18.6.2, a major security update, before stopping iOS 18.6 signing.

Apple has taken a significant step in enhancing the security and functionality of its iOS platform by stopping the signing of iOS 18.6. This move comes after the release of iOS 18.6.1 and iOS 18.6.2, which included crucial security updates and fixes for known vulnerabilities. By no longer signing iOS 18.6, Apple ensures that users have the latest security improvements and are not vulnerable to known attacks [2].

The iOS 18.6 update, released on July 29, addressed several key issues. It included bug fixes, security improvements, and a fix for a performance issue with the Photos app's Memories feature. Additionally, Apple made changes to how third-party app marketplaces are handled in the EU. The subsequent release of iOS 18.6.1 and iOS 18.6.2 provided major security updates, further solidifying the platform's security posture [2].

The stoppage of iOS 18.6 signing also coincides with Apple's decision to reintroduce the Blood Oxygen feature on its Apple Watch Series 9, Series 10, and Ultra 2 models in the United States. This feature, which was temporarily disabled due to a patent dispute, is now accessible through a software update. Users can update their paired iPhone to iOS 18.6.1 and their Apple Watch to watchOS 11.6.1 to access the redesigned Blood Oxygen feature [1].

The Blood Oxygen feature uses infrared light to estimate oxygen levels in the blood, helping users detect conditions such as sleep apnea or altitude-related issues. The reinstatement of this feature underscores Apple's strategic pivot in handling health-tech patents and highlights the delicate balance between innovation and intellectual property protection [1, 3].

Market reactions to these updates have been mixed. While Apple's shares ticked up modestly following the announcement, Masimo's stock dipped, reflecting the competitive tensions in the wearable health market. Tech enthusiasts and insiders have expressed optimism about the feature's return, enhancing the Watch's value proposition without requiring hardware upgrades [3].

Looking ahead, these updates may accelerate Apple's push into advanced health monitoring, such as rumored glucose tracking or enhanced ECG capabilities. However, they also raise questions about the sustainability of proprietary health tech in a litigious environment [3].

References:
[1] https://www.apple.com/newsroom/2025/08/an-update-on-blood-oxygen-for-apple-watch-in-the-us/
[2] https://www.macrumors.com/2025/08/22/apple-stops-signing-ios-18-6/
[3] https://www.webpronews.com/apple-reinstates-blood-oxygen-on-watch-via-iphone-update/