Markdown should be escaped when converting to XML

[thinxer]

Here:

https://github.com/edx/edx-platform/blob/master/common/lib/xmodule/xmodule/js/src/problem/edit.coffee#L191

This code (toXML) doesn't escape "&""<"">" to HTML entities, which may cause the resulted XML to be invalid.

[Slater-Victoroff]

@gwprice @mikigoyal Where did we land on escaping issues?

[gwprice]

@Slater-Victoroff I'm not sure what you mean. I was looking at escaping in the mako templates. I don't know anything about escaping functionality in coffee.

[IainNZ]

Bumping this issue - it really causes issues when giving R code examples in a class we're making.

[singingwolfboy]

Is this still a problem in the latest version of the codebase?