Apple has released OS X Yosemite 10.10.4 with stability, compatibility, and security improvements.
The OS X Yosemite 10.10.4 update improves the stability, compatibility, and security of your Mac, and is recommended for all users.
● Improves networking reliability
● Improves Migration Assistant reliability
● Addresses an issue that prevented certain external monitors from functioning properly
● Improves the reliability of upgrading iPhoto and Aperture libraries to Photos
● Improves reliability when syncing photos and videos to iCloud Photo Library
● Addresses an issue that caused Photos to quit unexpectedly after importing some Leica DNG files
● Resolves an issue that could delay outgoing email messages in Mail
For more detailed information about this update, please visit: http://support.apple.com/kb/HT204928
For detailed information about the security content of this update, please visit: http://support.apple.com/kb/HT1222
You can get the update by navigating to the Updates tab in the Mac App Store.