avoid infinite loops

lib/marked.js

@@ -285,6 +285,11 @@ block.token = function(src, tokens, top) {
       });
       continue;
     }
+
+    if (src) {
+      throw new
+        Error('Infinite loop on byte: ' + src.charCodeAt(0));
+    }
   }
 
   return tokens;
@@ -465,6 +470,11 @@ inline.lexer = function(src) {
       out += escape(cap[0]);
       continue;
     }
+
+    if (src) {
+      throw new
+        Error('Infinite loop on byte: ' + src.charCodeAt(0));
+    }
   }
 
   return out;
@@ -704,7 +714,15 @@ noop.exec = noop;
 
 function marked(src, opt) {
   setOptions(opt);
+  try {
     return parse(block.lexer(src));
+  } catch (e) {
+    e.message += '\nPlease report this to https://github.com/chjj/marked.';
+    if (marked.options.silent) {
+      return 'An error occured: ' + e.message;
+    }
+    throw e;
+  }
 }
 
 /**