text_area_tag not escaping content by default

rubyonrails-talk
1

I stumbled on the fact that text_area_tag does not HTML escape its content by default. For example:

  text_area_tag "body", "</textarea><script>alert('xss');<script>"

If you try that, you'll see that the content is inserted literally. Considering the fact that the tag helpers all encode their attribute values by default, does this surprise anyone else?

I found a ticket on this issue from a couple years ago from Chris Mear but it looks like it was dropped: http://dev.rubyonrails.org/ticket/5929

It seems like there were two main arguments against encoding:

1. backwards compatibility 2. some people depend on this behavior to allow HTML in their text area boxes

#2 I don't really understand. You can allow HTML...just escape it. It's equivalent to allowing HTML in a text field tag, no? You have to either know the value is sanitized or escape it.

#1 I can understand, but that's not a show-stopper, right? There have been numerous non-backwards-compatible changes adopted by introducing them slowing, providing config options, etc.

I'm guessing there's quite a few people using text_area_tag and assuming the content is being safely escaped by default. And every one of them is an XSS problem.

It's an issue with anything that uses content_tag, of course. Try this, for example:

  label_tag 'foo', "</lable><script>alert('xss2')</script>"

At the very least, are we amendable to adding a note in the FormTagHelper docs about the escaping rules?

2

I've posted a new ticket on Lighthouse with an up-to-date patch:

http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/2015-text_area_tag-should-escape-contents-by-default

I also noticed that the text_area method in FormHelper actually does escape its contents now, so text_area_tag probably should do the same for consistency's sake if nothing else.

Chris