noun, masculine/blɑ̃.sɛ̃/plural: blanc-seings
blanc-seing is masculine in French.
blank signature; a document so signed, a blank check etc.; carte blanche, license, free rein
“2021 (November 22), Agence France-Presse, "Kyle Rittenhouse dit qu’il soutient Black Lives Matter," La Presse” — The verdict shocked part of America, in whose view it offered carte blanche to white supremacists and armed groups.
From blanc (“white”) and seing (“signature”).