fix($sanitize): sanitize xml:base attributes

On Firefox there is a XSS vulnerability if a malicious attacker
can write into the `xml:base` attribute on an SVG anchor.

Thanks to Masato Kinugawa at Cure23

src/ngSanitize/sanitize.js

@@ -269,7 +269,7 @@ function $SanitizeProvider() {
                                      optionalEndTagElements);
 
   //Attributes that have href and hence need to be sanitized
-  var uriAttrs = toMap('background,cite,href,longdesc,src,xlink:href');
+  var uriAttrs = toMap('background,cite,href,longdesc,src,xlink:href,xml:base');
 
   var htmlAttrs = toMap('abbr,align,alt,axis,bgcolor,border,cellpadding,cellspacing,class,clear,' +
       'color,cols,colspan,compact,coords,dir,face,headers,height,hreflang,hspace,' +

test/ngSanitize/sanitizeSpec.js

@@ -327,6 +327,15 @@ describe('HTML', function() {
                    '<svg xmlns="http://www.w3.org/2000/svg"><a xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://example.com"></a></svg>');
     });
 
+    it('should sanitize SVG xml:base attribute values', function() {
+      expectHTML('<svg xmlns="http://www.w3.org/2000/svg"><a xml:base="javascript:alert(1)//" href="#"></a></svg>')
+        .toEqual('<svg xmlns="http://www.w3.org/2000/svg"><a href="#"></a></svg>');
+
+      expectHTML('<svg xmlns="http://www.w3.org/2000/svg"><a xml:base="https://example.com" href="#"></a></svg>')
+        .toEqual('<svg xmlns="http://www.w3.org/2000/svg"><a xml:base="https://example.com" href="#"></a></svg>');
+
+    });
+
     it('should sanitize unknown namespaced SVG attributes', function() {
       expectHTML('<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><a xlink:foo="javascript:alert()"></a></svg>')
         .toBeOneOf('<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><a></a></svg>',