--- a/netwerk/protocol/about/nsAboutCache.cpp
+++ b/netwerk/protocol/about/nsAboutCache.cpp
@@ -180,23 +180,27 @@ nsAboutCache::VisitNextStorage()
 void
 nsAboutCache::FireVisitStorage()
 {
     nsresult rv;
 
     rv = VisitStorage(mStorageName);
     if (NS_FAILED(rv)) {
         if (mLoadInfo) {
+            char* escaped = nsEscapeHTML(mStorageName.get());
             mBuffer.Append(
                 nsPrintfCString("<p>Unrecognized storage name '%s' in about:cache URL</p>",
-                                mStorageName.get()));
+                                escaped));
+            nsMemory::Free(escaped);
         } else {
+            char* escaped = nsEscapeHTML(mContextString.get());
             mBuffer.Append(
                 nsPrintfCString("<p>Unrecognized context key '%s' in about:cache URL</p>",
-                                mContextString.get()));
+                                escaped));
+            nsMemory::Free(escaped);
         }
 
         FlushBuffer();
 
         // Simulate finish of a visit cycle, this tries the next storage
         // or closes the output stream (i.e. the UI loader will stop spinning)
         OnCacheEntryVisitCompleted();
     }