When a Rapid Security Response (RSR) is successfully applied to an iPadOS device, the operating system version number shown in Settings > General > About is updated to include a single-letter identifier in parentheses. For example, if an RSR is applied to iPadOS 17.5.1, the version number would appear as iPadOS 17.5.1 (a). This letter indicates that a specific, targeted security update has been installed on top of the base OS version, without requiring a full OS update. This mechanism allows Apple to deliver critical security improvements more quickly.

B. The letters “.rsr” are not used in the user-facing version string; this is an incorrect format for identifying an applied RSR.

C. A single letter, not a digit, is used as the identifier for an applied Rapid Security Response.

D. The identifier “.eve” is not associated with Apple's Rapid Security Response updates or its versioning scheme.

1. Apple Support. (2024). About Rapid Security Responses for iOS

iPadOS

and macOS. Document HT213406. Retrieved from https://support.apple.com/en-us/HT213406.

Reference Point: The document explicitly states

"If a Rapid Security Response has been applied

a letter appears after the version number

for example: macOS 13.3.1 (a)." It provides a screenshot example for an iPhone showing "iOS 16.5.1 (c)

" confirming the same format for iOS and iPadOS.

2. Apple Inc. (May 2024). Apple Platform Security. Retrieved from https://help.apple.com/pdf/security/enUS/apple-platform-security-guide.pdf.

Reference Point: Page 31

"Rapid Security Responses" section. This section describes the purpose and mechanism of RSRs

stating they "deliver important security improvements between software updates." While it doesn't specify the version string format

it validates the existence and function of the RSR feature being tested.