Confluence has a built-in component for connecting to other remote systems via HTTP (the HttpRetrievalService). Internally, this is built on top of the Apache Commons HttpClient (http://hc.apache.org).

Some user-facing components of Confluence, such as the JIRA Issues Macro, depend on this service to connect to remote systems and retrieve data for display.

There is a bug/limitation in the current version of Confluence's HttpRetrievalService that makes it unable to communicate with remote servers configured to use HTTPS that only accept SSLv3 as the encryption algorithm.