just had a problem attaching #images to toots in my #mastodon instance. it always said "Oops! An unexpected error occurred."turned out, that my #CSP rule prohibited `blob:` images.
now it's running fine with
add_header Content-Security-Policy "default-src 'self' 'unsafe-inline'; img-src 'self' data: blob:";
mstdn.binfalse.de is one server in the network