CVE-2024-39899: PrivateBin allows shortening of URLs for other domains

In v1.5 we introduced the YOURLS server-side proxy. The idea was to allow using the YOURLs URL shortener without running the YOURLs instance without authentication and/or exposing the authentication token to the public, allowing anyone to shorten any URL. With the proxy mechanism, anyone can shorten any URL pointing to the configured PrivateBin instance. The vulnerability allowed other URLs to be shortened, as long as they contain the PrivateBin instance, defeating the limit imposed by the proxy.

Neither the confidentially of existing pastes on the server nor the configuration options including the YOURLs token are affected.