Issue on closing popup and showing message after doing any action in CiviCRM
Only that last line (starting with {"buttonName) should be present.  The rest looks like debugging code that was accidentally left in.

If this doesn't sound like something you may have done personally, try disabling extensions and re-enabling them one by one (or half at a time) until you've found the troublesome extension.

UPDATE: Since this code isn't in an extension, it may be in core.  I searched the codebase for the words "Object ID", which appear in your output - and for me they only appear in xml/schema/ACL/ACL.xml and CRM/ACL/DAO/ACL.php.  If you search YOUR codebase for the words "Object ID" you're bound to find them somewhere else.