...If you wish to allow HTML within untrusted user-input, but still want output to be free from XSS it is recommended that you make use of a HTML sanitiser that allows HTML tags to be whitelisted, like HTML Purifier. In both cases you should strongly consider employing defence-in-depth measures, like deploying a Content-Security-Policy (a browser security feature) so that your page is likely to be safe even if an attacker finds a vulnerability in one of the first lines of defence. Safe mode does not necessarily yield safe results when using extensions to Parsedown. Extensions should be evaluated on their own to determine their specific safety against XSS.