XML mode memory leak crash

Typing a certain sequence of characters in XML mode results in a memory leak/infinite loop which eventually crashes the page. To reproduce:

1. Go to https://ace.c9.io/build/kitchen-sink.html
2. Set the mode to XML
3. Delete the document's contents
4. Paste the following: ``
5. Watch the memory tab of Chrome Debugger to see the memory leak. The page will soon crash (it takes me about 45 seconds).

This bug is present in the current version of Ace, and at least as far back as Ace 1.2.3.
Crashes on Windows 7 and 10, in Chrome.