I don't know if I am the first to face this.
Back in WP 3.4 I guess we had the HTML feature enabled in caption. Now, in WP 3.5 whenever I try to add some caption like
We execute <span class="code">$sudo cat /etc/group</span>
It fails. I have checked with firebug and it seems for some strange reason, when the POST req is sent to ajax-admin.php, it comes up with 404 not found. Now, removing the characters /, >, < solves the issue. It is me anything doing wrong or is it a bug from WP or my host? Any ideas?