What is RSR?
A Rapid Security Response is a small Apple update that patches a security problem, often one Apple says may have been actively exploited, without waiting for the next numbered iOS, iPadOS or macOS release. Support arrived with iOS 16, iPadOS 16 and macOS Ventura. The first public RSRs shipped in May 2023 for iOS 16.4.1, iPadOS 16.4.1 and macOS 13.3.1, and they fixed flaws in WebKit, the engine behind Safari.
How to recognize one
An RSR adds a letter in parentheses to the version number, such as iOS 16.4.1 (a) or macOS 13.3.1 (a). On an iPhone, Settings > General > About shows the full version. RSRs are issued only for the latest OS version, and their fixes are rolled into the next standard update, after which the letter disappears.
RSRs vs. standard updates
| Feature | Rapid Security Response | Standard software update |
|---|---|---|
| Contents | Targeted security fixes | Security fixes, bug fixes and often new features |
| Size and install time | Small and quick | Larger, longer install |
| Version format | Letter suffix, such as (a) | New version number, such as 16.5 |
| Removal | Can be removed on the device | No simple rollback |
Settings and removal
- Automatic install: on iPhone and iPad, the option is under Settings > General > Software Update > Automatic Updates, labeled Security Responses & System Files. Macs have a matching option in Software Update settings.
- Removal: if an RSR causes a problem, it can be removed. On an iPhone, go to Settings > General > About, tap the iOS Version entry and choose Remove Security Response. The device returns to the base version, and the response can be reinstalled later or arrives as part of the next standard update.
A real-world example
In July 2023, Apple released iOS 16.5.1 (a) and a matching macOS RSR, then pulled them because the version string Safari reported caused some websites to stop working properly. Apple followed up with corrected releases labeled (c). This is the situation the removal option exists for: if a site or app breaks right after an RSR, removing the response restores the earlier behavior while the device stays on the same base version.
Apple has issued public RSRs only a few times, so most iPhones and Macs get their security fixes through standard numbered updates.
RSR on the CompTIA A+ exam
RSR is on the A+ acronym list and fits Core 2's macOS and mobile OS update topics. Know that:
- RSR expands to Rapid Security Response, and it is an Apple mechanism, not a Windows or Android one.
- A version number ending in a letter in parentheses, such as (a), means an RSR is installed.
- RSRs deliver urgent security fixes between full updates and can be removed if they cause problems.
- Microsoft's monthly security updates (Patch Tuesday) are a different, scheduled process.