WPMU duplicating users into different Sites.

Hi,

I found a possible security issue that is causing critical errors on my MultiSite.

If I as a “Super Admin” user, open in different web windows different sub-sites main pages (Site A, Site B and Site C) and try to “switch to” a “user1” of “Site D“, while I navigate as “user1” nothing happens (everything is ok).

But if during that process (before switching back) I just click on any of the “Site A, B or C” windows, the system automatically creates the same “user1” into those Sites. So finally I have the same “user1” created on all those Sites.

Maybe you know why this is happening?

Thank you very much.