In addition to OS X Yosemite 10.10.3 and iOS 8.3, released yesterday, Apple has made some more updates available to users / developers.

Xcode
in Apple

Version 11.4.1 (8.1 GB) Requires macOS 10.15.2 or superior
Version 6.3 includes Swift 1.2 and SDKs for OS X Yosemite 10.10.3 and iOS 8.3.
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Apple Configurator 1.7.2 brings compatibility patches with OS X 10.10.3, support for new payloads of configuration profiles and adjustments introduced in iOS 8.1.3 / 8.2 / 8.3, force arm detection on the Apple Watch, more restriction options, new IKEv2 certificate, new values and encryption keys.
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Apple also released the Security Update 2015-004, in separate versions for OS X Mavericks and OS X Mountain Lion bringing all (or most of) security fixes built into OS X Yosemite 10.10.3.