Bad Request when sending message to Extension PubSub

Yep, I meant “base 64 decoding” haha. Now I’m getting a 403 forbidden response, the body is a set of weird characters though:

"\u001f�\b\0\0\0\0\0\0\u0003,�1\n�0\u0010Dѫ,S�\u0010L�V��\u0004�(YE�\r$�\u0012�n4i�<�\u001b\u0012c�p\u0018C\\v�Ea��\u0004g�����M\n��ut�\u0012q#\fG��ښ�\"c8v�L\u001a2��R�h�?�f*�XG�\a�\v\0\0��\u0003\0�-�7�\0\0\0"

Probably missing some convertion here. However I’ve seen other users with this 403 responses too, wasn’t this because of testing locally?