Microsoft releases updates and patches on a regular basis to cover up any flaws or bugs that rear their ugly heads as time goes by. The most recent update fixes critical flaws in a number of apps, including Office.
From Computer World:
Microsoft fixed more than 40 vulnerabilities in its products Tuesday, including critical ones in Windows, Internet Explorer, Edge and Office.
The vulnerabilities are covered in 16 security bulletins, six of which are marked as critical and the rest as important. This puts the total number of Microsoft security bulletins for the past six months to more than 160, a six-month record for the past decade.