Is Markdown (with strip_tags) sufficient to stop XSS attacks?

Question

I\'m working on a web application that allows users to type short descriptions of items in a catalog. I\'m allowing Markdown in my textareas so users can do some HTML format

Answer 1

Here's a lovely example of why you need to sanitize the HTML after, not before:

Markdown code:

>  
>

Rendered as:

Now are you worried?