How do i get rid of an update notification on my app store application?

Question

the notification appeared since the unboxing of my brand new iMac. when i tried updating it shows someone else's apple id and i can't get rid of it.

Answer 1

You installed a hacked application, originally from the Mac App Store. It contains the receipt for a different application, downloaded from another account. You need to identify and remove the hacked application.
Triple-click the line of text below on this page to select it:
kMDItemAppStoreHasReceipt=1
Copy the selected text to the Clipboard (command-C).
In the Finder, press the key combination command-F to open a search window, or select
File ▹ Find
from the menu bar. In the search window, select
Search: This Mac
from the row of tokens below the toolbar. Below that is a popup menu initially showing Kind. From that menu, select  Other...
A sheet will drop down. In that sheet, select Raw Query and click OK or press return.
Now there will be a text box to the right of popup menu. Click in that box and paste (command-V).
The search window will show all the App Store products you've installed. Compare those search results with the list of your purchases from the App Store. To see the complete list, you may need to unhide hidden purchases. If any applications were download from the App Store using other Apple ID accounts that you know of, sign in to the store under each of those ID's and check the purchases.
If any of the items listed in the search window are not listed among your purchases in the App Store, move them to the Trash. You may be prompted for your administrator password. Empty the Trash.