Here is the relevant section in the changelog, I think:
"Change the default template handler from ERB to Raw.
Files without a template handler in their extension will be rendered using the raw handler instead of ERB.
Rafael Mendonça França"
I always give it a glance to the changelogs before trying to upgrade but this documented change didn't grab my attention enough to think that it might impact on my application.
There are a few performance/analytics/monitoring related scripts that are loaded directly in an inline script in one of my view layouts.
They are loaded like this:
<% unless params[:monitoring] || Rails.env.development? -%>
<%= render '/common/pingdomjs.js' %>
<% end -%>
After this change I had to move it to:
<%= render('/common/pingdomjs.js').html_safe %>
I think this is not an uncommon pattern and that maybe the need of such changes to non ERB files rendering should be highlighted in the Changelog to grab the reader's attention.
This is just a sugestion to improve the changelog before Rails 5 final is released in order to make the upgrade process smoother.