discourse/lib/validators/censored_words_validator.rb

class CensoredWordsValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    if !SiteSetting.censored_words.blank? &&
      !(censored_words = value.scan(/#{SiteSetting.censored_words}/i)).empty?

      record.errors.add(
        attribute, :contains_censored_words,
        censored_words: join_censored_words(censored_words)
      )
    elsif !SiteSetting.censored_pattern.blank? &&
      !(censored_words = value.scan(/#{SiteSetting.censored_pattern}/i)).empty?

      record.errors.add(
        attribute, :matches_censored_pattern,
        censored_words: join_censored_words(censored_words)
      )
    end
  end

  private

    def join_censored_words(censored_words)
      censored_words.map!(&:downcase)
      censored_words.uniq!
      censored_words.join(", ")
    end
end