Microsoft stated that Office 365 and Microsoft 365 services including Exchange Online, SharePoint Online, and OneDrive for Business will require versions of Office software that are still supported starting on October 13, 2020. This means that older versions such as Office 2010 and Office 2013 will start to see possible reliability and performance issues as they reach their end of support. For older versions that are no longer supported, patches that address bug issues, security updates, and new vulnerabilities will not be released. In a statement from Microsoft, “Organizations that use these older clients will almost certainly face an increased security risk and may find themselves out of compliance depending upon specific regional or industry requirements.”
Office 365 subscriptions currently have no end-of-life date, but Office 2010 and Office 2013 both have an end-of-life date of October 2020. Attackers will commonly use older, unsupported software to leverage attacks–knowing that new attack vectors will not be patched. Administrators are highly recommended to upgrade to newer software packages that will continue to have updates published for them. ZDNet recently reported that attackers are focusing more efforts on breaching Office 365 accounts because of the sensitivity of data that companies store in Office 365 and the increasing reliance that companies have on the service.
Source Article: https://www.bleepingcomputer.com/news/microsoft/office-365-services-will-drop-support-for-older-office-clients/