Wikimedia Bugzilla is closed!

at several locations in the code there is
> QDesktopServices::openUrl(QString(<xxx>+<yyy>));
where xxx and yyy two strings. Apart from creating a new string from a string,
openUrl only accepts a QUrl. Thus QT automatically casts the whole url-QString to QUrl using presumably
> QUrl::QUrl ( const QString & url )
which automatically percent encode all characters (of the whole url).

On some locations there are parameters also percent encoded prior adding them to the url which results in double encoding.

using the following in our huggle.pro prevents the implicit cast for the future (or similiar for non-qmake)
> DEFINES += QT_NO_URL_CAST_FROM_STRING

see also https://github.com/huggle/huggle3-qt-lx/pull/68