Steps to reproduce:

1. Create a new article;
2. On an an XML block field (used "body"), insert a custom tag of type "factbox";
3. On the custom tag popup window's "title" field, entered HTML code such as "<a href="http://ez.no">Test link</a>";
4. Click "OK", effectively inserting the new custom tag into the "body" field;
5. Click on the "Disable editor" button;
6. The resulting HTML code is this:

<custom name="factbox">Test linkattribute_separationalign|right&quot;&gt;


factbox</custom>