diff --git a/src/Handler/Utils.hs b/src/Handler/Utils.hs
index 0aaddd6cb..ccfd7d3e0 100644
--- a/src/Handler/Utils.hs
+++ b/src/Handler/Utils.hs
@@ -37,6 +37,7 @@ import Control.Monad.Logger
 sendThisFile :: DBFile -> Handler TypedContent
 sendThisFile File{..}
   | Just fileContent' <- fileContent = do
+      setCSPSandbox
       setContentDisposition' . Just $ takeFileName fileTitle
       let cType = simpleContentType (mimeLookup $ pack fileTitle) <> "; charset=utf-8"
       respondSourceDB cType $
@@ -45,7 +46,8 @@ sendThisFile File{..}
 
 sendFileReference :: forall file a. HasFileReference file => file -> Handler a
 sendFileReference (view (_FileReference . _1) -> fRef@FileReference{..}) = do
-  when (is _Just fileReferenceContent) $
+  when (is _Just fileReferenceContent) $ do
+    setCSPSandbox
     setContentDisposition' . Just $ takeFileName fileReferenceTitle
   let cType = simpleContentType (mimeLookup $ pack fileReferenceTitle) <> "; charset=utf-8"
   join . runDB $ respondFileConditional Nothing cType fRef
@@ -77,6 +79,7 @@ serveSomeFiles' archiveName source = do
     []         -> notFound
     [file]     -> either sendFileReference sendThisFile file
     _moreFiles -> do
+      setCSPSandbox
       setContentDisposition' $ Just archiveName
       respondSourceDB typeZip $ do
         let zipComment = T.encodeUtf8 $ pack archiveName
@@ -97,6 +100,7 @@ serveZipArchive' archiveName source = do
   case results of
     []         -> notFound
     _moreFiles -> do
+      setCSPSandbox
       setContentDisposition' $ Just archiveName
       respondSourceDB typeZip $ do
         let zipComment = T.encodeUtf8 $ pack archiveName
diff --git a/src/Utils.hs b/src/Utils.hs
index b403810b7..646e7afb5 100644
--- a/src/Utils.hs
+++ b/src/Utils.hs
@@ -1052,6 +1052,9 @@ setContentDisposition cd (fmap pack -> mFName) = replaceOrAddHeader (decodeUtf8
       | otherwise
       = toPathPiece cd
 
+setCSPSandbox :: MonadHandler m => m ()
+setCSPSandbox = replaceOrAddHeader "Content-Security-Policy" "sandbox;"
+
 ------------------
 -- Cryptography --
 ------------------