No "Open" button in Internet Explorer When Clicking on Attachments
Symptoms
When using Internet Explorer (IE) version 8 or later and Confluence 4.3.2 (possibly above), when clicking on an attachment, the 
button is not present. Users must Save the file first, before accessing it.
Diagnosis
This problem has been reported as a bug that can be tracked here: CONF-26994 - Getting issue details... STATUS
This bug has been resolved in Confluence 4.3.5. This KB article remains here for historical purposes.
Cause
The cause of the problem is that a new HTTP header was introduced in version 4.3.2 as a security patch. This header (X-Download-Options: noopen) is handled more strictly by Internet Explorer than other browsers, thus the Open button is missing in this case.
Resolution
Upgrade to Confluence 4.3.5 and above, as the bug was resolved in this version.
Workaround
One possible workaround is to use a different browser, however this is not suitable in all environments. Another way to get around this problem is to remove this HTTP header. This can be done in several ways, that mostly depend on your local setup. Since, in many cases, people are Using Apache with mod_proxy or NGINX, using this method you can remove this header:
Apache / mod_proxy
- Make sure you have Apache's native mod_header module enabled.
- Modify your Apache configuration where you have defined the <Location> tag for Confluence to include the following on a separate line between <Location> and </Location>: Header unset X-Download-Options
- Restart Apache
NGINX
Add the following to remove the header to your configuration:
proxy_set_header X-Download-Options "";- Restart NGINX
Please note that by implementing this solution you are risking that the effects of the applied security patch is not in place anymore, you shall consider the risk in your own environment and only apply this workaround at your own risk.