Ruby on Rails "invalid byte sequence in UTF-8" due to bot

Add this line to your Gemfile, then run bundle in your terminal:

gem "handle_invalid_percent_encoding_requests"

This solution is based on Henrik's answer, turned into a Rails Engine gem.

So you don't have to piece together the comments in my other reply, this is what I'm doing now – I've seen no errors for 24 hours, so it looks very promising:

Add rack-utf8_sanitizer to your Gemfile:

gem 'rack-utf8_sanitizer'

and run

bundle

Put this middleware in app/middleware/handle_invalid_percent_encoding.rb and rename the class HandleInvalidPercentEncoding (because ExceptionApp is a bit too general).

In the config block of config/application.rb do:

require "#{Rails.root}/app/middleware/handle_invalid_percent_encoding.rb"


# NOTE: These must be in this order relative to each other.
# HandleInvalidPercentEncoding just raises for encoding errors it doesn't cover,
# so it must run after (= be inserted before) Rack::UTF8Sanitizer.
config.middleware.insert 0, HandleInvalidPercentEncoding
config.middleware.insert 0, Rack::UTF8Sanitizer  # from a gem

Deploy. Done.

(app happens to be the location for middleware in the project I'm working on, but I'd probably prefer lib. Whatever. Either should work.)