diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
index 0669b3b..cf8de6c 100644
--- a/Source/WebKit/ChangeLog
+++ b/Source/WebKit/ChangeLog
@@ -1,3 +1,21 @@
+2019-07-12  Chris Dumez  <cdumez@apple.com>
+
+        Regression(macOS Catalina): Cannot quick look html documents in Mail
+        https://bugs.webkit.org/show_bug.cgi?id=199754
+        <rdar://problem/51304961>
+
+        Reviewed by Geoff Garen.
+
+        If the client asks us to load a file URL but does not provide a resource path, WebKit
+        would fallback to issuing a sandbox extension for /. This no longer works on mac OS
+        Catalina and it would thus fail to load the file.
+
+        To address the issue, if the attempt to create a sandbox extension for / fails, we now
+        fall back to issuing one for the file's baseURL (path of containing folder).
+
+        * UIProcess/WebPageProxy.cpp:
+        (WebKit::WebPageProxy::maybeInitializeSandboxExtensionHandle):
+
 2019-07-12  Michael Catanzaro  <mcatanzaro@igalia.com>
 
         WebBackForwardListItem::setPageState should receive pageState by rvalue reference
diff --git a/Source/WebKit/UIProcess/WebPageProxy.cpp b/Source/WebKit/UIProcess/WebPageProxy.cpp
index 24f1e60..2af0e81 100644
--- a/Source/WebKit/UIProcess/WebPageProxy.cpp
+++ b/Source/WebKit/UIProcess/WebPageProxy.cpp
@@ -1058,9 +1058,16 @@
     // Inspector resources are in a directory with assumed access.
     ASSERT_WITH_SECURITY_IMPLICATION(!WebKit::isInspectorPage(*this));
 
-    // FIXME: universal file read access should be set if the sandbox extension is successfully created: rdar://problem/52357508.
-    SandboxExtension::createHandle("/", SandboxExtension::Type::ReadOnly, sandboxExtensionHandle);
-    willAcquireUniversalFileReadSandboxExtension(process);
+    if (SandboxExtension::createHandle("/", SandboxExtension::Type::ReadOnly, sandboxExtensionHandle)) {
+        willAcquireUniversalFileReadSandboxExtension(process);
+        return;
+    }
+
+    // We failed to issue an universal file read access sandbox, fall back to issuing one for the base URL instead.
+    auto baseURL = URL(URL(), url.baseAsString());
+    auto basePath = baseURL.fileSystemPath();
+    if (!basePath.isNull() && SandboxExtension::createHandle(basePath, SandboxExtension::Type::ReadOnly, sandboxExtensionHandle))
+        m_process->assumeReadAccessToBaseURL(*this, baseURL);
 }
 
 #if !PLATFORM(COCOA)