Q: Security Update 2015-003: what is it

What does it state in the information provided? It's likely updates for malware. Just found this: Apple security updates - Apple Support.

For info:

https://support.apple.com/kb/DL1800?locale=en_IS

There's nothing big in these security updates, they just patch bugs that Apple find relating to security. However, you should install it ASAP since they fix security vulnerabilities in your system.

Howdy,

As per:

About Security Update 2015-003 - Apple Support

https://support.apple.com/en-us/HT204563

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Security Update 2015-003

iCloud Keychain

Available for: OS X Yosemite v10.10.2

Impact: An attacker with a privileged network position may be able to execute arbitrary code

Description: Multiple buffer overflows existed in the handling of data during iCloud Keychain recovery. These issues were addressed through improved bounds checking.

CVE-ID

CVE-2015-1065 : Andrey Belenko of NowSecure

IOSurface

Available for: OS X Yosemite v10.10.2

Impact: A malicious application may be able to execute arbitrary code with system privileges

Description: A type confusion issue existed in IOSurface's handling of serialized objects. The issue was addressed through additional type checking.

CVE-ID

CVE-2015-1061 : Ian Beer of Google Project Zero

Note: Security Update 2015-003 includes the content of Security Update 2015-002