Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
What version of Mac OS X are you using ? Click on bthe Apple icon and select About This Mac. You can find the version of OS X in there
When did this problem start ?
This usually happens if Safari application is corrupted. We may need to reinstall the OS X. But first we can restart your Mac in Safe Mode and reset Safari. Restart your Mac and immediately hold down Shift key on your keyboard for 20 seconds and this will boot into Safe Mode. It may take up to 20 minutes to boot into Safe mode.
Don't open Safari yet. In Safe Mode, click on Finder icon on dock. Then hold down Option key on your keyboard, click on Go menu and select Library. This will take you to the library folder of your home folder. Trash Safari folder. Then open Caches folder and trash Safari folder or folder related to Safari. Go back to Library, then open Preferences folder and trash the file 'com.apple.Safari.plist' and other files related to Safari.
Now, download the application named Malwarebytes Anti Malware application from here and do a scan --> https://www.malwarebytes.org/antimalware/mac/
You can download it from another browser like Chrome or Firefox. If you don't have another browser, then download it from another computer, copy it to a flash drive and run it on your Mac. Then scan and if it find anything, delete them all. Open Safari.
Please let me know if that didn't work, so we can continue troubleshooting.
You said an update might have caused it. So if the above steps didn't work, then I want you to reinstall the OS X. This will replace the corrupted update with a fresh one.
Reinstalling OS X won't delete any of your files. It will just replace the corrupted system files with new one and that should fix the problem.
Restart your Mac and immediately hold down Command and R keys at the same time for 15 seconds and this will boot your Mac to the Mac OS X Utilities screen. From there, click Reinstall Mac OS X. Then follow the instructions to reinstall your Mac OS X.
If that didn't work, then restart your Mac and immediately hold down Command, Option and R keys at the same time for 15 seconds and this will boot your Mac to installation screen. Follow the onscreen instructions to reinstall.
The update has crashed the system files. Reinstalling the OS X should work. Ok, we can continue tomorrow.
If it still not working, then please let me know and we will continue to troubleshoot it.