"New Document" element is not properly translated, where should I report that?

I use elementary OS 0.3.2 Freya, a GNU/Linux distribution based on Ubuntu 14.04.

On LibreOffice 4.2.8.2, the “New Document” element in the application menu list (see screenshot below) is not translated into French.

Imgur

Where should I report that bug?

Please report a bug. It may also be worth mentioning this issue on the localisation (l10n) mailing list, although the l10n team may ask you to raise a bug report in any case.