When composing a message and using the "Insert an existing attachment" feature, if you choose to go to a page of your choice at the bottom ( Page 1of 99), and after clicking Go, the site's home page and default skin open. See the image.

If pages with attachments are opened with a choice of 2,3,4, etc. no issues.

The same action in an editor, for example in a forum post, works correctly.

Is this just for me or is it an bug in 4.6.8?

Check to ensure mod_security is not causing a block on that page. This is most likely what is causing the issue

3 hours ago, Marc Stridgen said:

Check to ensure mod_security is not causing a block on that page. This is most likely what is causing the issue

Disable mod_security does not solve this issue.

Are you seeing anything show up in console when you try this?

This is all content in console

Do you have any custom redirects/rewrites on the server? If so, you will want to temporarily remove those to see if they are involved. Something on the server is causing the page to be redirected so you will want to remove all custom items that are not a part of our software to eliminate these.

1 hour ago, Jim M said:

Do you have any custom redirects/rewrites on the server? If so, you will want to temporarily remove those to see if they are involved. Something on the server is causing the page to be redirected so you will want to remove all custom items that are not a part of our software to eliminate these.

No, I have no custom redirects. If there is something on the server, the same function should be behaved in this way when posting in a forum topic. But in a forum when creating a post or topic, this feature works perfectly without any issues.

6 minutes ago, Adlago said:

No, I have no custom redirects. If there is something on the server, the same function should be behaved in this way when posting in a forum topic. But in a forum when creating a post or topic, this feature works perfectly without any issues.

Unfortunately, FTP'ing into your server, I am seeing that your .htaccess has a redirect and a lot of custom items set in it. I would advise temporarily removing these to see if they impact it.

If that does not help, please update the admin credentials on file and we can review further.

26 minutes ago, Jim M said:

Unfortunately, FTP'ing into your server, I am seeing that your .htaccess has a redirect and a lot of custom items set in it. I would advise temporarily removing these to see if they impact it.

If that does not help, please update the admin credentials on file and we can review further.

There was an outdated redirect in my htaccess file, I removed it - but no change. The issue is available.
Your ACP access account is active.
Now I've tested this profile and attached enough images through it so that when using a bulk mail editor you can see this feature and issue.

Unfortunately, the admin credentials on file are not working as provided. Please test and update.

7 minutes ago, Jim M said:

Unfortunately, the admin credentials on file are not working as provided. Please test and update.

Try now

Thank you, I was able to distinguish something which likely is a bug on our end as I am able to reproduce this in this case. I have submitted a bug report and a fix will be available in a future release. Thank you again for reporting!

This issue has been resolved in 4.6.10 beta 1. Feel free to give this a try, or await the full release if you prefer

Perfect !!!