diff --git a/pkgs/applications/networking/mailreaders/thunderbird/default.nix b/pkgs/applications/networking/mailreaders/thunderbird/default.nix
index 5c566514e41..c5c75c79ba8 100644
--- a/pkgs/applications/networking/mailreaders/thunderbird/default.nix
+++ b/pkgs/applications/networking/mailreaders/thunderbird/default.nix
@@ -351,5 +351,6 @@ stdenv.mkDerivation rec {
     ];
     platforms = platforms.linux;
     license = licenses.mpl20;
+    knownVulnerabilities = ["EOL.  Firefox 78.15 fixes some vulnerabilities: https://www.mozilla.org/en-US/security/advisories/mfsa2021-44/"];
   };
 }