Hello,
I'm sorry that you are having trouble with posting images in your forums. The error message you received is a common security feature to prevent spammers from posting malicious links. However, I'd be happy to help you resolve this issue.
One way to bypass this issue is to modify the link to the image you are trying to post. Instead of using the "http" prefix, try using "hXXp" instead. This should allow you to post the link without triggering the security feature.
Another solution would be to upload the image to an image hosting site such as imgur.com or postimages.org, and then embed the image URL in your post.
If you continue to have trouble, please contact the forum moderators for further assistance.
I hope this helps!