diff --git a/lib/default.js b/lib/default.js
index 1452ed3..55c506c 100644
--- a/lib/default.js
+++ b/lib/default.js
@@ -159,6 +159,10 @@ function safeAttrValue(tag, name, value, cssFilter) {
         value.substr(0, 8) === "https://" ||
         value.substr(0, 7) === "mailto:" ||
         value.substr(0, 4) === "tel:" ||
+        value.substr(0, 11) === "data:image/" ||
+        value.substr(0, 6) === "ftp://" ||
+        value.substr(0, 2) === "./" ||
+        value.substr(0, 3) === "../" ||
         value[0] === "#" ||
         value[0] === "/"
       )