SECURITY: escape display names

Ensure we escape the display names before passing it to the regexp used to update
quotes whenever a user change their display name.

lib/quote_rewriter.rb

@@ -6,17 +6,20 @@ class QuoteRewriter
   end
 
   def rewrite_raw_username(raw, old_username, new_username)
+    escaped_old_username = Regexp.escape(old_username)
     pattern =
       Regexp.union(
-        /(?<pre>\[quote\s*=\s*["'']?.*username:)#{old_username}(?<post>\,?[^\]]*\])/i,
+        /(?<pre>\[quote\s*=\s*["'']?.*username:)#{escaped_old_username}(?<post>\,?[^\]]*\])/i,
-        /(?<pre>\[quote\s*=\s*["'']?)#{old_username}(?<post>\,?[^\]]*\])/i,
+        /(?<pre>\[quote\s*=\s*["'']?)#{escaped_old_username}(?<post>\,?[^\]]*\])/i,
       )
 
     raw.gsub(pattern, "\\k<pre>#{new_username}\\k<post>")
   end
 
   def rewrite_cooked_username(cooked, old_username, new_username, avatar_img)
-    pattern = /(?<=\s)#{PrettyText::Helpers.format_username(old_username)}(?=:)/i
+    formatted_old_username = PrettyText::Helpers.format_username(old_username)
+    escaped_old_username = Regexp.escape(formatted_old_username)
+    pattern = /(?<=\s)#{escaped_old_username}(?=:)/i
 
     cooked
       .css("aside.quote")
@@ -42,13 +45,17 @@ class QuoteRewriter
   end
 
   def rewrite_raw_display_name(raw, old_display_name, new_display_name)
-    pattern = /(?<pre>\[quote\s*=\s*["'']?)#{old_display_name}(?<post>\,[^\]]*username[^\]]*\])/i
+    escaped_old_display_name = Regexp.escape(old_display_name)
+    pattern =
+      /(?<pre>\[quote\s*=\s*["'']?)#{escaped_old_display_name}(?<post>\,[^\]]*username[^\]]*\])/i
 
     raw.gsub(pattern, "\\k<pre>#{new_display_name}\\k<post>")
   end
 
   def rewrite_cooked_display_name(cooked, old_display_name, new_display_name)
-    pattern = /(?<=\s)#{PrettyText::Helpers.format_username(old_display_name)}(?=:)/i
+    formatted_old_display_name = PrettyText::Helpers.format_username(old_display_name)
+    escaped_old_display_name = Regexp.escape(formatted_old_display_name)
+    pattern = /(?<=\s)#{escaped_old_display_name}(?=:)/i
 
     cooked
       .css("aside.quote")

spec/jobs/change_display_name_spec.rb

@@ -3,7 +3,11 @@
 RSpec.describe Jobs::ChangeDisplayName do
   before { stub_image_size }
 
-  let(:user) { Fabricate(:user, username: "codinghorror", name: "Jeff") }
+  let(:username) { "codinghorror" }
+  let(:old_display_name) { "|| Jeff ||" }
+  let(:new_display_name) { "|| Mr. Atwood ||" }
+
+  let(:user) { Fabricate(:user, username: username, name: old_display_name) }
   let(:topic) { Fabricate(:topic, user: user) }
   let!(:post) { create_post(post_attributes.merge(topic_id: topic.id)) }
 
@@ -11,25 +15,25 @@ RSpec.describe Jobs::ChangeDisplayName do
   let(:avatar_url) { user.avatar_template_url.gsub("{size}", "48") }
 
   let(:post_attributes) { { raw: <<~RAW } }
-    [quote="Jeff, post:1, topic:#{quoted_post.topic.id}, username:codinghorror"]
+    [quote="#{old_display_name}, post:1, topic:#{quoted_post.topic.id}, username:#{username}"]
     quoted post
     [/quote]
   RAW
 
   let(:revised_post_attributes) { { raw: <<~RAW } }
-    [quote="Jeff, post:1, topic:#{quoted_post.topic.id}, username:codinghorror"]
+    [quote="#{old_display_name}, post:1, topic:#{quoted_post.topic.id}, username:#{username}"]
     quoted post
     [/quote]
     Forgot something.
   RAW
 
-  let(:args) { { user_id: user.id, old_name: "Jeff", new_name: "Mr. Atwood" } }
+  let(:args) { { user_id: user.id, old_name: old_display_name, new_name: new_display_name } }
 
   describe "#execute" do
     context "when the renamed user has been quoted" do
       it "rewrites the raw quote display name" do
         expect { described_class.new.execute(args) }.to change { post.reload.raw }.to(<<~RAW.strip)
-          [quote="Mr. Atwood, post:1, topic:#{quoted_post.topic.id}, username:codinghorror"]
+          [quote="#{new_display_name}, post:1, topic:#{quoted_post.topic.id}, username:#{username}"]
           quoted post
           [/quote]
         RAW
@@ -38,10 +42,10 @@ RSpec.describe Jobs::ChangeDisplayName do
       it "rewrites the cooked quote display name" do
         expect { described_class.new.execute(args) }.to change { post.reload.cooked }.to(
           match_html(<<~HTML.strip),
-          <aside class="quote no-group" data-username="codinghorror" data-post="1" data-topic="#{quoted_post.topic.id}">
+          <aside class="quote no-group" data-username="#{username}" data-post="1" data-topic="#{quoted_post.topic.id}">
           <div class="title">
           <div class="quote-controls"></div>
-          <img loading="lazy" alt="" width="24" height="24" src="#{avatar_url}" class="avatar"> Mr. Atwood:</div>
+          <img loading="lazy" alt="" width="24" height="24" src="#{avatar_url}" class="avatar"> #{new_display_name}:</div>
           <blockquote>
           <p>quoted post</p>
           </blockquote>
@@ -58,7 +62,7 @@ RSpec.describe Jobs::ChangeDisplayName do
         expect { described_class.new.execute(args) }.to change {
           post.reload.revisions[0].modifications["raw"][0]
         }.to(<<~RAW.strip)
-          [quote="Mr. Atwood, post:1, topic:#{quoted_post.topic.id}, username:codinghorror"]
+          [quote="#{new_display_name}, post:1, topic:#{quoted_post.topic.id}, username:#{username}"]
           quoted post
           [/quote]
           RAW