@misc{ wiki:xxx, author = "Wikimedia Commons", title = "File:Accession Treaty 2003 FA Austria.svg --- Wikimedia Commons{,} the free media repository", year = "2023", url = "https://commons.wikimedia.org/w/index.php?title=File:Accession_Treaty_2003_FA_Austria.svg&oldid=780425928", note = "[Online; accessed 4-July-2024]" }
\usepackage{url}
somewhere in the preamble) which tends to give much more nicely formatted web addresses, the following may be preferred:
@misc{ wiki:xxx, author = "Wikimedia Commons", title = "File:Accession Treaty 2003 FA Austria.svg --- Wikimedia Commons{,} the free media repository", year = "2023", url = "\url{https://commons.wikimedia.org/w/index.php?title=File:Accession_Treaty_2003_FA_Austria.svg&oldid=780425928}", note = "[Online; accessed 4-July-2024]" }