See last line of this diff: https://fr.wikipedia.org/w/index.php?title=T%C3%A9l%C3%A9com_SudParis&diff=next&oldid=97023702 .
Steps to reproduce, as provided by user: Seudo.
- Go to https://fr.wikipedia.org/wiki/Cumul_des_mandats_en_France - you don't need to save later
- Click on Modifier
- Place the cursor after the words « exercice simultané de mandats » (5th line, I think)
- Click "Plus->Référence"
- Write something in the dialog, i.e. "toto."
- Save the reference
- Click at the left or at the right of the newly added reference
- Watch pawns multiplyin' as you keep clicking.
I was able to reproduce this as well, but only with FF (exactly like Seudo), only in the actual article - not in my sandbox - and only clicking at the left of the word. The user reports instead that this might happen at any point in the page.
My edits in the sandbox could not reproduce the issue but generated https://bugzilla.wikimedia.org/show_bug.cgi?id=54341 instead.