I have tested in my 5.2.5 test site that it adds <vb:literal> tags around the code in Ad modules. I don't know if this was intended but it looks like this was implemented recently in the past one or two versions. I assume this was intended for vBCloud only and not for self-hosted. So I guess this has the same issue as the Text Only flag in css_additional template (
http://tracker.vbulletin.com/browse/VBV-16683).
Btw, the added literal tags can be easily bypassed by closing and opening it and putting your code in between.
Code:
</vb:literal>
--- Your Ad module code here ---
<vb:literal>
First post updated to add this workaround. This workaround will probably work in vBCloud too.