uploader said from de.wikipedia.org replaceing commons.wikimedia.org with de.wikipedia.org revealed the following text on which the tag here is based. public doman - selbst erstellt mit MS Paint und pngout Following the link to the only page that linked to the file <a href="https://de.wikipedia.org/wiki/Tallinn" class="extiw" title="de:Tallinn">de:Tallinn</a> revealed that this appears to be the flag of Tallinn.
Unknown author<span style="display: none;">Unknown author</span>
Unknown source<span style="display: none;">Unknown source</span>