XSS using crafted markdown link

Current version of Framaslides is vulnerable to an XSS attack

How to reproduce

  • A malicious user creates a presentation
  • In a the markdown editor, (s)he enters: [my link](javascript:alert('xss'))
  • The targeted user visits the slides in presentation mode and clicks on the malicious link
  • The JS payload is executed

This issue doesn't seems to affect the editor part.