diff --git a/src/applications/maniphest/xaction/ManiphestTaskCoverImageTransaction.php b/src/applications/maniphest/xaction/ManiphestTaskCoverImageTransaction.php
--- a/src/applications/maniphest/xaction/ManiphestTaskCoverImageTransaction.php
+++ b/src/applications/maniphest/xaction/ManiphestTaskCoverImageTransaction.php
@@ -33,6 +33,20 @@
 
     $object->setProperty('cover.filePHID', $file->getPHID());
     $object->setProperty('cover.thumbnailPHID', $xform->getPHID());
+
+    // Connect the Transform to the original file.
+    // In this way the user can change the permissions of the original File
+    // and this Transform automatically reflects these policies.
+    $xtransformed = id(new PhabricatorTransformedFile())
+      ->setOriginalPHID($file_phid)
+      ->setTransformedPHID($xform->getPHID())
+      ->setTransform($xform_key)
+      ->save();
+
+    // As side-effect, attach the Cover Image to the Object,
+    // otherwise it may be invisible to other participants.
+    // This is always successful.
+    $file->attachToObject($object->getPHID());
   }
 
   public function getTitle() {
diff --git a/src/applications/project/controller/PhabricatorProjectCoverController.php b/src/applications/project/controller/PhabricatorProjectCoverController.php
--- a/src/applications/project/controller/PhabricatorProjectCoverController.php
+++ b/src/applications/project/controller/PhabricatorProjectCoverController.php
@@ -35,6 +35,7 @@
 
     $xactions = array();
 
+    // Set the new Cover Image.
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(ManiphestTaskCoverImageTransaction::TRANSACTIONTYPE)
       ->setNewValue($file->getPHID());