1 files changed, 5 insertions, 0 deletions
diff --git a/image/imgLoader.cpp b/image/imgLoader.cpp
index 3545c5be2..5e5ee7829 100644
--- a/image/imgLoader.cpp
+++ b/image/imgLoader.cpp
@@ -2558,6 +2558,11 @@ imgLoader::GetMimeTypeFromContent(const char* aContents,
                               !memcmp(aContents, "\000\000\002\000", 4))) {
     aContentType.AssignLiteral(IMAGE_ICO);
 
+  // WebPs always begin with RIFF, a 32-bit length, and WEBP.
+  } else if (aLength >= 12 && !memcmp(aContents, "RIFF", 4) &&
+                              !memcmp(aContents + 8, "WEBP", 4)) {
+    aContentType.AssignLiteral(IMAGE_WEBP);
+
   } else {
     /* none of the above?  I give up */
     return NS_ERROR_NOT_AVAILABLE;