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diff --git a/lib/banzai/filter/dollar_math_post_filter.rb b/lib/banzai/filter/dollar_math_post_filter.rb
new file mode 100644
index 00000000000..94d1b4bcb48
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+++ b/lib/banzai/filter/dollar_math_post_filter.rb
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+# frozen_string_literal: true
+
+# Generated HTML is transformed back to GFM by:
+# - app/assets/javascripts/behaviors/markdown/marks/math.js
+# - app/assets/javascripts/behaviors/markdown/nodes/code_block.js
+module Banzai
+  module Filter
+    # HTML filter that implements our dollar math syntax, one of three filters:
+    # DollarMathPreFilter, DollarMathPostFilter, and MathFilter
+    #
+    class DollarMathPostFilter < HTML::Pipeline::Filter
+      # Based on the Pandoc heuristics,
+      # https://pandoc.org/MANUAL.html#extension-tex_math_dollars
+      #
+      # Handle the $...$ and $$...$$ inline syntax in this filter, after markdown processing
+      # but before post-handling of escaped characters.  Any escaped $ will have been specially
+      # encoded and will therefore not interfere with the detection of the dollar syntax.
+
+      # Corresponds to the "$...$" syntax
+      DOLLAR_INLINE_PATTERN = %r{
+        (?<matched>\$(?<math>(?:\S[^$\n]*?\S|[^$\s]))\$)(?:[^\d]|$)
+      }x.freeze
+
+      # Corresponds to the "$$...$$" syntax
+      DOLLAR_DISPLAY_INLINE_PATTERN = %r{
+        (?<matched>\$\$\ *(?<math>[^$\n]+?)\ *\$\$)
+      }x.freeze
+
+      # Order dependent. Handle the `$$` syntax before the `$` syntax
+      DOLLAR_MATH_PIPELINE = [
+        { pattern: DOLLAR_DISPLAY_INLINE_PATTERN, style: :display },
+        { pattern: DOLLAR_INLINE_PATTERN, style: :inline }
+      ].freeze
+
+      # Do not recognize math inside these tags
+      IGNORED_ANCESTOR_TAGS = %w[pre code tt].to_set
+
+      def call
+        process_dollar_pipeline
+
+        doc
+      end
+
+      def process_dollar_pipeline
+        doc.xpath('descendant-or-self::text()').each do |node|
+          next if has_ancestor?(node, IGNORED_ANCESTOR_TAGS)
+
+          node_html = node.to_html
+          next unless node_html.match?(DOLLAR_INLINE_PATTERN) ||
+            node_html.match?(DOLLAR_DISPLAY_INLINE_PATTERN)
+
+          temp_doc = Nokogiri::HTML.fragment(node_html)
+
+          DOLLAR_MATH_PIPELINE.each do |pipeline|
+            temp_doc.xpath('child::text()').each do |temp_node|
+              html = temp_node.to_html
+              temp_node.content.scan(pipeline[:pattern]).each do |matched, math|
+                html.sub!(matched, math_html(math: math, style: pipeline[:style]))
+              end
+
+              temp_node.replace(html)
+            end
+          end
+
+          node.replace(temp_doc)
+        end
+      end
+
+      private
+
+      def math_html(math:, style:)
+        "<code data-math-style=\"#{style}\">#{math}</code>"
+      end
+    end
+  end
+end