Hello,
I find where is my problem.
You are right, it's necessary to replace $urlvars = $item->params->get( 'urlvars' ); to $urlvars = $item->getParams()->get('urlvars'); in plugins/system/cck/cck.php
But with that my problem is not resolved.
In fact, when user want to access is profil, the url has some errors like that :
https://mysite.fr/component/cck/form/user.html?id=(number)&_amp;Itemid=(number)&_amp;return=aHR...
If I replace &_amp; by & in the url, that works ! It's logical.
The problem is now : why &_amp instead of &, and where correcting that ?
Thanks for an idea :)
PS : there is no underscore in fact, but it's not possible to write &_amp; without underscore in this forum ;)