open letter

US /ˌoʊ.pən ˈlet̬.ɚ/
UK /ˌoʊ.pən ˈlet̬.ɚ/
"open letter" picture
1.

carta abierta

a letter of protest or appeal addressed to a particular person or group but intended for general publication

:
The activists published an open letter to the government.
Los activistas publicaron una carta abierta al gobierno.
Her open letter about climate change went viral.
Su carta abierta sobre el cambio climático se hizo viral.