Microsoft has removed Equation Editor from Microsoft Office, citing “security issues with its implementation” Affected users may be tempted to forego this Office update and by extension all future Office updates. Microsoft suggested affected users can “edit Equation editor 3.0 equations without security issues” with Wiris Suite’s MathType, a commercial application that costs $97 ($57 academic) Microsoft gave up on the idea of continuing manual support for the tool after being faced with 8 (eight!)* new vulnerabilities.”]
Source: https://blog.0patch.com/2018/01/bringing-abandoned-equation-editor-back.html