Can't post, am I retarded? (yes)

[somenobody2]

Firefox
trying to post to /co/ and suddenly not working despite not changing anything afaik
I try to reply normally I get this in console:
Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://sys.4chan.org/co/post. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing). Status code: 403.
Using Original Form I get sent to a blank page at https://sys.4chan.org/co/post with this in console:

What obvious FAQ did I miss?

[birdbrid]

I'm getting this problem too and looking for a fix but haven't found one yet. Am I also retarded?