For many years, Microsoft Word has had a feature called Equation Editor that let people, well, edit equations in Word documents. In November, it was discovered that Equation Editor had a flaw that had gone undiscovered for 17 years that let hackers into your system. Microsoft fixed the flaw in November, but it now seems that Equation Editor is still being used as a gateway for hackers. So in the latest update, Microsoft has simply removed Equation Editor altogether.
If you rely on Equation Editor, here’s Microsoft’s suggestion:
You can insert and edit new equations using the editor built into Office version 2007 or later. For more information about inserting and editing equations, see Write, insert, or change an equation. However, you will not be able to edit existing equations that were inserted using Equation Editor 3.0 in that manner.
Alternatively, the third-party app MathType enables you to edit Equation Editor 3.0 equations without security issues. MathType is now part of the Wiris Suite. You can download a free MathType 30-day trial at: http://www.wiris.com/equation_editor/microsoft