Recently my instance of Vanilla Forums stoped authenticating users via Facebook. Instead, the error message "UniqueID is required" is shown in the authentication page.
After some research I found this blog post, this github issue and this pull request.
For now I fixed the function getAccessToken()
replacing this:
if (strpos(val('content_type', $Info, ''), '/javascript') !== false) {
$Tokens = json_decode($Contents, true);
} else {
parse_str($Contents, $Tokens);
}
with this:
if (strpos(val('content_type', $Info, ''), '/javascript') !== false) {
$Tokens = json_decode($Contents, true);
} else if (strpos(val('content_type', $Info, ''), '/json') !== false) {
$Tokens = json_decode($Contents, true);
} else {
parse_str($Contents, $Tokens);
}
Since the Pull Request was merged a few days ago, the next release should fix this.