If I were a betting person, I would put my stakes on gdk-pixbuf (https://github.com/snapcrafters/vscode/blob/master/files/bin/wrapper#L36)

If that is part of code's environment, whatever it calls will leak that env into the callee...

sergiusens@umbar:~$ snap run --shell code
sergiusens@umbar:~$ cd $SNAP
sergiusens@umbar:/snap/code/25$ cat electron-launch 
#!/usr/bin/env bash

# On Fedora $SNAP is under /var and there is some magic to map it to /snap.
# We need to handle that case and reset $SNAP
SNAP=$(echo $SNAP | sed -e "s|/var/lib/snapd||g")

if [ "$SNAP_ARCH" == "amd64" ]; then
  ARCH="x86_64-linux-gnu"
elif [ "$SNAP_ARCH" == "armhf" ]; then
  ARCH="arm-linux-gnueabihf"
elif [ "$SNAP_ARCH" == "arm64" ]; then
  ARCH="aarch64-linux-gnu"
else
  ARCH="$SNAP_ARCH-linux-gnu"
fi

export XDG_CACHE_HOME=$SNAP_USER_COMMON/.cache
if [[ -d $SNAP_USER_DATA/.cache && ! -e $XDG_CACHE_HOME ]]; then
  # the .cache directory used to be stored under $SNAP_USER_DATA, migrate it
  mv $SNAP_USER_DATA/.cache $SNAP_USER_COMMON/
fi
mkdir -p $XDG_CACHE_HOME

# Gdk-pixbuf loaders
export GDK_PIXBUF_MODULE_FILE=$XDG_CACHE_HOME/gdk-pixbuf-loaders.cache
export GDK_PIXBUF_MODULEDIR=$SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/2.10.0/loaders
if [ -f $SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/gdk-pixbuf-query-loaders ]; then
  $SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/gdk-pixbuf-query-loaders > $GDK_PIXBUF_MODULE_FILE
fi

# Create $XDG_RUNTIME_DIR if not exists (to be removed when https://pad.lv/1656340 is fixed)
[ -n "$XDG_RUNTIME_DIR" ] && mkdir -p $XDG_RUNTIME_DIR -m 700

exec "$@"
sergiusens@umbar:/snap/code/25$ if [ "$SNAP_ARCH" == "amd64" ]; then
>   ARCH="x86_64-linux-gnu"
> elif [ "$SNAP_ARCH" == "armhf" ]; then
>   ARCH="arm-linux-gnueabihf"
> elif [ "$SNAP_ARCH" == "arm64" ]; then
>   ARCH="aarch64-linux-gnu"
> else
>   ARCH="$SNAP_ARCH-linux-gnu"
> fi
sergiusens@umbar:/snap/code/25$ 
sergiusens@umbar:/snap/code/25$ export XDG_CACHE_HOME=$SNAP_USER_COMMON/.cache
sergiusens@umbar:/snap/code/25$ if [[ -d $SNAP_USER_DATA/.cache && ! -e $XDG_CACHE_HOME ]]; then
>   # the .cache directory used to be stored under $SNAP_USER_DATA, migrate it
>   mv $SNAP_USER_DATA/.cache $SNAP_USER_COMMON/
> fi
sergiusens@umbar:/snap/code/25$ mkdir -p $XDG_CACHE_HOME
sergiusens@umbar:/snap/code/25$ 
sergiusens@umbar:/snap/code/25$ # Gdk-pixbuf loaders
sergiusens@umbar:/snap/code/25$ export GDK_PIXBUF_MODULE_FILE=$XDG_CACHE_HOME/gdk-pixbuf-loaders.cache
sergiusens@umbar:/snap/code/25$ export GDK_PIXBUF_MODULEDIR=$SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/2.10.0/loaders
sergiusens@umbar:/snap/code/25$ if [ -f $SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/gdk-pixbuf-query-loaders ]; then
>   $SNAP/usr/lib/$ARCH/gdk-pixbuf-2.0/gdk-pixbuf-query-loaders > $GDK_PIXBUF_MODULE_FILE
> fi
sergiusens@umbar:/snap/code/25$ firefox
ExceptionHandler::GenerateDump cloned child 570327
ExceptionHandler::SendContinueSignalToChild sent continue signal to child
ExceptionHandler::WaitForContinueSignal waiting for continue signal...
sergiusens@umbar:/snap/code/25$ unset GDK_PIXBUF_MODULE_FILE 
sergiusens@umbar:/snap/code/25$ unset GDK_PIXBUF_MODULEDIR 
sergiusens@umbar:/snap/code/25$ firefox

###!!! [Child][MessageChannel] Error: (msgtype=0x370135,name=PContent::Msg_DetachBrowsingContext) Closed channel: cannot send/recv


As you can see, env exported gets a crash, next, after unsetting, everything is fine.