sanitize

This sanitize helper will html encode all tags and strip all attributes that aren't specifically allowed.

It also strips href/src tags with invalid protocols, like javascript: especially. It does its best to counter any tricks that hackers may use, like throwing in unicode/ascii/hex values to get past the javascript: filters. Check out the extensive test suite.

<%= sanitize @article.body %>

You can add or remove tags/attributes if you want to customize it a bit. See ActionView::Base for full docs on the available options. You can add tags/attributes for single uses of sanitize by passing either the :attributes or :tags options:

Normal Use

<%= sanitize @article.body %>

Custom Use (only the mentioned tags and attributes are allowed, nothing else)

<%= sanitize @article.body, tags: %w(table tr td), attributes: %w(id class style) %>

Add table tags to the default allowed tags

class Application < Rails::Application
  config.action_view.sanitized_allowed_tags = ['table', 'tr', 'td']
end

Remove tags to the default allowed tags

class Application < Rails::Application
  config.after_initialize do
    ActionView::Base.sanitized_allowed_tags.delete 'div'
  end
end

Change allowed default attributes

class Application < Rails::Application
  config.action_view.sanitized_allowed_attributes = ['id', 'class', 'style']
end

Please note that sanitizing user-provided text does not guarantee that the resulting markup is valid (conforming to a document type) or even well-formed. The output may still contain e.g. unescaped '<', '>', '&' characters and confuse browsers.