Word is displaying field codes instead of formatted fields. To toggle this mode, press Alt-F9 (Windows) or Option-F9/Option-Fn-F9 (Mac). You can also Select All, right-click, and choose Toggle Field Codes in the context menu, or change the setting from the Word preferences.

If you see this repeatedly, check your Word settings to ensure that “Show Field Codes instead of Values” is not checked.

When using Track Changes, Word will sometimes show you the changed and original versions of changed field codes. If this occurs, click “Accept” twice to quickly accept the changed citations and hide the field codes again.