Yeah, I thought it was a custom app at first but that error comes from the CMS API to create/update a record. Specifically the code that handles files for a custom upload field:
elseif ( $field->type === 'Upload' )
{
$multiple = $field->is_multiple;
$imageOnly = ( isset( $field->extra[ 'type' ] ) AND $field->extra[ 'type' ] === 'image' );
$extensions = \is_array( $field->allowed_extensions ) ? $field->allowed_extensions : array();
/* Did they meet the api parameter type requirement (the field must be an object) */
if ( !\is_array( \IPS\Request::i()->fields[ $field->id ] ) )
{
throw new \IPS\Api\Exception( 'UPLOAD_FIELD_NOT_OBJECT', '1S306/E', 400 );
}
It it was working before I guess the API code is old while the forum was updated at some point and the API code changed but the external code was not updated.