Uses GULAppEnvironmentUtil.isAppExtension

FirebaseStorage.podspec

@@ -42,6 +42,7 @@ Firebase Storage provides robust, secure file uploads and downloads from Firebas
   s.dependency 'FirebaseCore', '~> 10.0'
   s.dependency 'FirebaseCoreExtension', '~> 10.0'
   s.dependency 'GTMSessionFetcher/Core', '>= 2.1', '< 4.0'
+  s.dependency 'GoogleUtilities/Environment', '~> 7.12'  
 
   s.test_spec 'ObjCIntegration' do |objc_tests|
     objc_tests.scheme = { :code_coverage => true }

FirebaseStorage/Sources/StorageUploadTask.swift

@@ -14,6 +14,12 @@
 
 import Foundation
 
+#if SWIFT_PACKAGE
+  @_implementationOnly import GoogleUtilities_Environment
+#else
+  @_implementationOnly import GoogleUtilities
+#endif // SWIFT_PACKAGE
+
 #if COCOAPODS
   import GTMSessionFetcher
 #else
@@ -88,7 +94,7 @@ import Foundation
         uploadFetcher.uploadFileURL = fileURL
         uploadFetcher.comment = "File UploadTask"
 
-        if Bundle.main.bundlePath.hasSuffix(".appex") {
+        if GULAppEnvironmentUtil.isAppExtension() {
           uploadFetcher.useBackgroundSession = false
         }
       }

Package.swift

@@ -1161,6 +1161,7 @@ let package = Package(
         "FirebaseCore",
         "FirebaseCoreExtension",
         .product(name: "GTMSessionFetcherCore", package: "gtm-session-fetcher"),
+        .product(name: "GULEnvironment", package: "GoogleUtilities"),
       ],
       path: "FirebaseStorage/Sources"
     ),