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 +33,15 @@
 
     $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 is reflecting these.
+    $xtransformed = id(new PhabricatorTransformedFile())
+      ->setOriginalPHID($file_phid)
+      ->setTransformedPHID($xform->getPHID())
+      ->setTransform($xform_key)
+      ->save();
   }
 
   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
@@ -35,10 +35,42 @@
 
     $xactions = array();
 
+    // Set the Image Cover.
     $xactions[] = id(new ManiphestTransaction())
       ->setTransactionType(ManiphestTaskCoverImageTransaction::TRANSACTIONTYPE)
       ->setNewValue($file->getPHID());
 
+    // Attach the Cover Image to the Task.
+    // Base case: handling a new file (supported):
+    //   If you are the author of the new File, that File is probably private
+    //   as default, so, you attach, to make it visible to Task participants.
+    // Future case: already-existing file (currently unsupported):
+    //   If you are the author of an already-existing file, that may be
+    //   already attached to this Object.
+    //   This is currently not supported from the UX but may be supported
+    //   later, checking for potential errors related to double-attach.
+    // Unknown future cases:
+    //   A non-author may want to attach a semi-private already-existing file
+    //   to make it somehow "more visible" than before without authorization
+    //   from the original author.
+    //   It is probably quite foolish to try to prevent this kind of things,
+    //   since, if you can see something, indeed you can copy-pasta that.
+    //   Anyway, since this use-case is unknown,
+    //   we are a bit strict, requiring to be the author of that file,
+    //   before sharing that as Task cover image.
+    //   If you want to support this, and omit this check, join the Task :)
+    // https://we.phorge.it/T15163
+    if ($file->getAuthorPHID() === $viewer->getPHID()) {
+      $template = $object->getApplicationTransactionTemplate();
+      $attach_mode = PhabricatorFileAttachment::MODE_ATTACH;
+      $xactions[] = id(clone $template)
+        ->setTransactionType(PhabricatorTransactions::TYPE_FILE)
+        ->setNewValue(
+          array(
+            $file_phid => $attach_mode,
+          ));
+    }
+
     $editor = id(new ManiphestTransactionEditor())
       ->setActor($viewer)
       ->setContinueOnMissingFields(true)