Ergänzung zu eben: Mit der Änderung der Zugriffsrechte der genannten Dateien des Ordners gm/javascript/jquery läuft das Update auf 2.6.0.0 ordnungsgemäss durch, der Shop (Kundenoberfläche) läuft so weit auch.
Allerdings ist in der Version 2.6.0.0. die Admin-Oberfläche geändert, wie im Installationsmanual beschrieben, und wenn ich mich als admin einlogge und "Gambio-Admin" wähle, kriege ich nur einen weißen Schirm. Wenn ich im Browser die Entwicklertools einblende, erhalte ich einen ganzen Rattenschwanz von Zugriffsfehlern:

https://webshop.fosar-bludorf.com/ad...-admin.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS.../vendor.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad.../vendor.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...require.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...ild/jse.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad...-admin.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad.../vendor.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad...logo-white.png Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...require.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...ild/jse.min.js Failed to load resource: the server responded with a status of 403 (Forbidden)
jquery-ui-datepicker.js:1773 Uncaught ReferenceError: jQuery is not defined
at jquery-ui-datepicker.js:1773
gm_counter.js:18 Uncaught ReferenceError: $ is not defined
at gm_counter.js:18
start.php?v2.6.0.0:1
Uncaught ReferenceError: jQuery is not defined
at eval (eval at <anonymous> (jquery.tooltip.pack.js:15), <anonymous>:1:4340)
at jquery.tooltip.pack.js:15
GMFavMaster.js:20
Uncaught ReferenceError: $ is not defined
at new GMFavMaster (GMFavMaster.js:20)
at start.php?v2.6.0.0:91
start.php?v2.6.0.0:97
Uncaught ReferenceError: $ is not defined
at start.php?v2.6.0.0:97
admin_javascript.js.php:280
Uncaught ReferenceError: jQuery is not defined
at admin_javascript.js.php:280
start.php?v2.6.0.0:254
Uncaught ReferenceError: $ is not defined
at start.php?v2.6.0.0:254
start.php?v2.6.0.0:609
Uncaught ReferenceError: $ is not defined
at start.php?v2.6.0.0:609

https://webshop.fosar-bludorf.com/ad...logo-white.png Failed to load resource: the server responded with a status of 403 (Forbidden)
gm_counter.js:59 Uncaught ReferenceError: $ is not defined
at gm_get_content (gm_counter.js:59)
at onload (start.php?v2.6.0.0:10)

https://webshop.fosar-bludorf.com/ad...-admin.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/ad...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)
https://webshop.fosar-bludorf.com/JS...vendor.min.css Failed to load resource: the server responded with a status of 403 (Forbidden)

Ich gehe davon aus, dass das auch wieder das 660 -> 666 - Problem ist, und werde versuchen, die Rechte manuell anzupassen. Nur - welche nächsten Rechte werden dann verletzt sein? So langsam wird das selbst für einen erfahrenen Computerbenutzer nicht nur mühsam, sondern auch undurchschaubar.