We know anyone can write his/her own extension for libreoffice .
Is there any procedure to prevent the hacker hide the virus at the extension?
I am afraid hacker through the extension to hack our important IT system.
You should avoid allowing users to download extensions or documents that contain macros from untrusted sources.
Perhaps there are some power users within your organisation that could be trusted to examine the code of an extension or document with macros to check if they contain anything malicious.
Dose extension download from libreoffice.org safe?
I means that Is any procedure to confirm clean for upload to lifeoffice.org.
or If we announce any extension from libreoffice.org is safe, Is it OK?
I think the risk is low for libreoffice.org but still not guaranteed. So far as I know there is no screening of macros or extensions. You would need to trust the site member creating the posting. I’d recommend you still inspect the code or test first in a sandbox. I’ve been trying “sandboxie”, there might be other similar applications.