Yep. If you don't know the language, it's best not to pretend you do.

I've done this kind of thing, even if I think it's likely they speak English. (I speak zero Japanese here.) It's just polite and you never know who's going to be reading it first.

> Google翻訳を使用しました。問題が発生した場合はお詫び申し上げます。貴社のウェブサイトにコンピュータセキュリティ上の問題が見つかりました。詳細は下記をご覧ください。ありがとうございます。

> I have found a computer security issue on your website. Here are details. Thank you.