who does make XDG_CONFIG_HOME directory (with inappropriate permissions) ?

Hello,

I am maintaining the package wxmaxima. I am currently bringing tests to the package.
I have notice that when the XDG_CONFIG_HOME directory (~/.config by default) does exist,
wxmaxima creates it but with inappropriates permissions.
For illustration, if a Sid schroot environment I do:

$ export XDG_CONFIG_HOME=$HOME/XDG_CONFIG_HOME
$ rm -rf $HOME/XDG_CONFIG_HOME
$ xvfb-run -a wxmaxima --version

then the directory ~/XDG_CONFIG_HOME is indeed created, but with inappropriate permissions:

$ ls -ld ~/XDG_CONFIG_HOME

gives

dr-------T 2 username usergroup 4096 Aug  1 19:47 /home/jgmb/XDG_CONFIG_HOME/

Right now, I have no idea who makes the directory. Is it a script somewhere or
the underlying wxWidgets library or something else ?

Any hint is welcome,
thanks in advance,
Jerome