From 7e8ea49bfb6b1c9620d6059f181915ebb3d18cbb Mon Sep 17 00:00:00 2001
From: Levi Broderick <levib@microsoft.com>
Date: Mon, 6 Jul 2026 17:00:21 -0700
Subject: [PATCH 1/2] Clarify regex warnings

---
 .../src/System/Text/RegularExpressions/Regex.cs    | 14 ++++++--------
 .../System/Text/RegularExpressions/RegexOptions.cs |  2 +-
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/Regex.cs b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/Regex.cs
index 6ffb0d3fb3683e..60790fb89acbd6 100644
--- a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/Regex.cs
+++ b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/Regex.cs
@@ -19,14 +19,12 @@ namespace System.Text.RegularExpressions
     /// Represents an immutable regular expression. Also contains static methods that
     /// allow use of regular expressions without instantiating a Regex explicitly.
     /// </summary>
-    /// <remarks>
-    /// <para>
-    /// The <see cref="Regex"/> class represents the .NET regular expression engine.
-    /// It can be used to quickly parse large amounts of text to find specific character patterns;
-    /// to extract, edit, replace, or delete text substrings; and to add the extracted strings to a
-    /// collection to generate a report.
-    /// </para>
-    /// </remarks>
+    /// <remarks><format type="text/markdown"><![CDATA[
+    /// The <xref:System.Text.RegularExpressions.Regex> class represents the .NET regular expression engine. It can be used to quickly parse large amounts of text to find specific character patterns; to extract, edit, replace, or delete text substrings; and to add the extracted strings to a collection to generate a report.
+    ///
+    /// > [!WARNING]
+    /// > Unrestricted use of this class with untrusted input can subject applications to [denial-of-service attacks](https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS). Consult [Best practices for regular expressions in .NET](https://learn.microsoft.com/dotnet/standard/base-types/best-practices-regex) for guidance on how to safely use this class with untrusted input.
+    /// ]]></format></remarks>
     /// <related type="Article" href="https://learn.microsoft.com/dotnet/standard/base-types/regular-expression-language-quick-reference">.NET Regular Expression Language</related>
     /// <related type="Article" href="https://learn.microsoft.com/dotnet/standard/base-types/regular-expression-options">Regular Expression Options</related>
     /// <related type="Article" href="https://learn.microsoft.com/dotnet/standard/base-types/best-practices">Best Practices for Regular Expressions</related>
diff --git a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
index 73fed871e37ff6..a6a6a198a5db3f 100644
--- a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
+++ b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
@@ -122,7 +122,7 @@ enum RegexOptions
 
         /// <summary>
         /// Enable matching using an approach that avoids backtracking and guarantees linear-time processing
-        /// in the length of the input. For more information, see the
+        /// in the length of the input. For more information, see the "Non-Backtracking mode" section in the
         /// <see href="https://learn.microsoft.com/dotnet/standard/base-types/regular-expression-options">
         /// Regular Expression Options</see> article.
         /// </summary>

From 3a2d5a8a68111698f367d763e1d20b942b9069b3 Mon Sep 17 00:00:00 2001
From: Levi Broderick <GrabYourPitchforks@users.noreply.github.com>
Date: Mon, 6 Jul 2026 17:08:04 -0700
Subject: [PATCH 2/2] Fixed typo

---
 .../src/System/Text/RegularExpressions/RegexOptions.cs          | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
index a6a6a198a5db3f..3f90cd190aadc3 100644
--- a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
+++ b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexOptions.cs
@@ -122,7 +122,7 @@ enum RegexOptions
 
         /// <summary>
         /// Enable matching using an approach that avoids backtracking and guarantees linear-time processing
-        /// in the length of the input. For more information, see the "Non-Backtracking mode" section in the
+        /// in the length of the input. For more information, see the "NonBacktracking mode" section in the
         /// <see href="https://learn.microsoft.com/dotnet/standard/base-types/regular-expression-options">
         /// Regular Expression Options</see> article.
         /// </summary>