Issues with MathML

In my testing to migrate a Planet instance to Pptlink, I've seen that feeds with MathML content (or at least that's the common feature in the three feeds) will make the planet misrender, with the visible side effect of the sidebar getting pushed to the footer.

I wonder if this is something in my setup, XML::Parser or what, but it did raise a concern of feeds being able to break the look of Planet Debian if the parser doesn't like some content. I have looked over open issues against XML::Parser and haven't seen anything relevant, but even if this apparent MathML was fixed, I am concerned that erroneous or malicious content can just make Planet Debian break enough that it becomes unreadable. Maybe there's need for more sanitizacion here.

Wouter, if you want to look at this particular issue, which may or may not affect PDO in the case of MathML showing up, you can check https://planet.igalia.com/ptlink. The offending feeds are Andy, Brian and Fréderic, all of which currently contain MathML markup.