From the info page on apple (linked elsewhere here but https://support.apple.com/en-us/HT201224 https://support.apple.com/en-us/HT201224 and (no discussion: htt

From the info page on apple (linked elsewhere here but https://support.apple.com/en-us/HT201224 https://support.apple.com/en-us/HT201224 and (no discussion: https://news.ycombinator.com/item?id=35776738 https://news.ycombinator.com/item?id=35776738)) >They deliver important security improvements between software updates — for example, improvements to the Safari web browser, the WebKit framework stack, or other critical system libraries. They may also be used to mitigate some security issues more quickly, such as issues that might have been exploited or reported to exist "in the wild." I believe they are vague on purpose (and because they're Apple) but it does not strike me as something strictly limited to affecting just Safari, especially given the libraries may be used elsewhere. ETA: To further quote from https://support.apple.com/guide/deployment/manage-rapid-security-responses-dep93ff7ea78/web https://support.apple.com/guide/deployment/manage-rapid-secu...: >Rapid Security Responses that involve the operating system require the device to restart. On macOS, the updated operating system content may be made available to Safari and its associated processes with just a relaunch of those processes, though a restart is required to make this content broadly available to the rest of the operating system.