--- a/toolkit/components/reputationservice/ApplicationReputation.cpp
+++ b/toolkit/components/reputationservice/ApplicationReputation.cpp
@@ -633,16 +633,17 @@ static const char* const kBinaryFileExte
     ".shar", // Linux shell
     ".shb", // Windows
     ".shs", // Windows shell
     ".shtml", // HTML
     ".shtm", // HTML
     ".sht", // HTML
     //".sldm", // MS PowerPoint
     //".sldx", // MS PowerPoint
+    ".slk", // MS Excel
     ".slp", // Linux package
     ".smi", // Mac disk image
     ".sparsebundle", // Mac disk image
     ".sparseimage", // Mac disk image
     ".spl", // Adobe Flash
     //".squashfs",
     ".svg",
     ".swf", // Adobe Flash