diff --git a/osu.Game.Tests/Chat/MessageFormatterTests.cs b/osu.Game.Tests/Chat/MessageFormatterTests.cs
index ebfa9bd8b7..3c35dc311f 100644
--- a/osu.Game.Tests/Chat/MessageFormatterTests.cs
+++ b/osu.Game.Tests/Chat/MessageFormatterTests.cs
@@ -26,6 +26,16 @@ namespace osu.Game.Tests.Chat
             MessageFormatter.WebsiteRootUrl = originalWebsiteRootUrl;
         }
 
+        [Test]
+        public void TestUnsupportedProtocolLink()
+        {
+            Message result = MessageFormatter.FormatMessage(new Message { Content = "This is a gopher://really-old-protocol we don't support." });
+
+            Assert.AreEqual(result.Content, result.DisplayContent);
+            Assert.AreEqual(1, result.Links.Count);
+            Assert.AreEqual("gopher://really-old-protocol", result.Links[0].Url);
+        }
+
         [Test]
         public void TestBareLink()
         {
diff --git a/osu.Game/OsuGame.cs b/osu.Game/OsuGame.cs
index 5565fa7ef3..bd33ab6545 100644
--- a/osu.Game/OsuGame.cs
+++ b/osu.Game/OsuGame.cs
@@ -16,6 +16,7 @@ using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Bindables;
 using osu.Framework.Configuration;
+using osu.Framework.Extensions;
 using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Framework.Extensions.TypeExtensions;
 using osu.Framework.Graphics;
@@ -406,6 +407,16 @@ namespace osu.Game
             if (url.StartsWith('/'))
                 url = $"{API.APIEndpointUrl}{url}";
 
+            if (!url.CheckIsValidUrl())
+            {
+                Notifications.Post(new SimpleErrorNotification
+                {
+                    Text = $"The URL {url} has an unsupported or dangerous protocol and will not be opened.",
+                });
+
+                return;
+            }
+
             externalLinkOpener.OpenUrlExternally(url, bypassExternalUrlWarning);
         });