From 78f3ed55ce429f7ac1e4148e0ef4d83f81e9eac7 Mon Sep 17 00:00:00 2001
From: Asherah Connor <aconnor@gitlab.com>
Date: Wed, 19 Nov 2025 16:04:49 +1100
Subject: [PATCH 1/4] Failing spec for frontmatter parser eating extras

---
 .../wiki_pages/front_matter_parser_spec.rb    | 28 +++++++++++++++++--
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/spec/lib/gitlab/wiki_pages/front_matter_parser_spec.rb b/spec/lib/gitlab/wiki_pages/front_matter_parser_spec.rb
index eb403b1fc940cb..67b955e473d5be 100644
--- a/spec/lib/gitlab/wiki_pages/front_matter_parser_spec.rb
+++ b/spec/lib/gitlab/wiki_pages/front_matter_parser_spec.rb
@@ -9,7 +9,7 @@
   let(:end_divider) { '---' }
 
   let(:with_front_matter) do
-    <<~MD
+    <<~MD.rstrip
     ---
     a: 1
     b: 2
@@ -35,7 +35,7 @@ def have_correct_front_matter
       it do
         is_expected.to have_attributes(
           front_matter: have_correct_front_matter,
-          content: content + "\n",
+          content: content,
           error: be_nil
         )
       end
@@ -53,6 +53,28 @@ def have_correct_front_matter
       end
     end
 
+    context 'the content itself appears to contain frontmatter' do
+      let(:content) do
+        <<~MD.rstrip
+        ---
+        custom: frontmatter
+        ---
+
+        Yay!
+        MD
+      end
+
+      let(:raw_content) { with_front_matter }
+
+      it do
+        is_expected.to have_attributes(
+          front_matter: have_correct_front_matter,
+          content: content,
+          error: be_nil
+        )
+      end
+    end
+
     context 'there is no front_matter' do
       let(:raw_content) { content }
 
@@ -67,7 +89,7 @@ def have_correct_front_matter
       it do
         is_expected.to have_attributes(
           front_matter: have_correct_front_matter,
-          content: content + "\n",
+          content: content,
           reason: be_nil
         )
       end
-- 
GitLab


From ee333f611d22b72baf4c846424ecffb68b8a64d6 Mon Sep 17 00:00:00 2001
From: Asherah Connor <aconnor@gitlab.com>
Date: Wed, 19 Nov 2025 16:04:49 +1100
Subject: [PATCH 2/4] FrontMatterParser should strip only one frontmatter

Anything after the one we insert is part of the user content.
---
 lib/gitlab/wiki_pages/front_matter_parser.rb | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/lib/gitlab/wiki_pages/front_matter_parser.rb b/lib/gitlab/wiki_pages/front_matter_parser.rb
index 3fd62771a90bdf..f796aa6ff0486c 100644
--- a/lib/gitlab/wiki_pages/front_matter_parser.rb
+++ b/lib/gitlab/wiki_pages/front_matter_parser.rb
@@ -105,9 +105,7 @@ def parse_front_matter_block
       end
 
       def strip_front_matter_block
-        Gitlab::FrontMatter::PATTERN_UNTRUSTED_REGEX.replace_gsub(wiki_content) do
-          ''
-        end
+        Gitlab::FrontMatter::PATTERN_UNTRUSTED_REGEX.replace(wiki_content, '')
       end
     end
   end
-- 
GitLab


From f84dbfd5348b98194366f77de097847ee729e3b8 Mon Sep 17 00:00:00 2001
From: Asherah Connor <aconnor@gitlab.com>
Date: Wed, 19 Nov 2025 16:44:32 +1100
Subject: [PATCH 3/4] Failing spec for extra newline after frontmatter start
 with CRLF

---
 .../banzai/filter/front_matter_filter_spec.rb | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/spec/lib/banzai/filter/front_matter_filter_spec.rb b/spec/lib/banzai/filter/front_matter_filter_spec.rb
index 81da8bb52f802f..72f772d9d96197 100644
--- a/spec/lib/banzai/filter/front_matter_filter_spec.rb
+++ b/spec/lib/banzai/filter/front_matter_filter_spec.rb
@@ -43,6 +43,26 @@
     end
   end
 
+  it "doesn't insert an extra preceding newline when faced with CRLF line endings" do
+    content = <<~MD.gsub("\n", "\r\n")
+      ---
+      foo: :foo_symbol
+      bar: :bar_symbol
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include '---'
+      expect(output).to include "```yaml:frontmatter\nfoo: :foo_symbol"
+    end
+  end
+
   it 'converts TOML frontmatter to a fenced code block' do
     content = <<~MD
       +++
-- 
GitLab


From 9884760c631e3326d656a5a5b2e684b2d3233cb6 Mon Sep 17 00:00:00 2001
From: Asherah Connor <aconnor@gitlab.com>
Date: Wed, 19 Nov 2025 16:04:49 +1100
Subject: [PATCH 4/4] UntrustedRegexp's BACKSLASH_R consumes \r\n in preference
 to \r

It will never match \r\n otherwise, so \r\n becomes in effect two
newlines.
---
 lib/gitlab/untrusted_regexp.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/gitlab/untrusted_regexp.rb b/lib/gitlab/untrusted_regexp.rb
index 006681654f315b..95a1d02e87fcd2 100644
--- a/lib/gitlab/untrusted_regexp.rb
+++ b/lib/gitlab/untrusted_regexp.rb
@@ -18,7 +18,7 @@ class UntrustedRegexp
 
     # recreate Ruby's \R metacharacter
     # https://ruby-doc.org/3.2.2/Regexp.html#class-Regexp-label-Character+Classes
-    BACKSLASH_R = '(\n|\v|\f|\r|\x{0085}|\x{2028}|\x{2029}|\r\n)'
+    BACKSLASH_R = '(\n|\v|\f|\r\n|\r|\x{0085}|\x{2028}|\x{2029})'
 
     delegate :===, :source, to: :regexp
 
-- 
GitLab