BigBlueButton is an open-source virtual classroom. BigBlueButton prior to versions 2.6.12 and 2.7.0-rc.1 is vulnerable to Server-Side Request Forgery (SSRF). This issue is a bypass of CVE-2023-33176. A patch in versions 2.6.12 and 2.7.0-rc.1 disabled follow redirect at `httpclient.execute` since the software no longer has to follow it when using `finalUrl`. There are no known workarounds. We recommend upgrading to a patched version of BigBlueButton.

BigBlueButton is an open source virtual classroom designed to help teachers teach and learners learn. In affected versions are affected by a Server-Side Request Forgery (SSRF) vulnerability. In an `insertDocument` API request the user is able to supply a URL from which the presentation should be downloaded. This URL was being used without having been successfully validated first. An update to the `followRedirect` method in the `PresentationUrlDownloadService` has been made to validate all URLs to be used for presentation download. Two new properties `presentationDownloadSupportedProtocols` and `presentationDownloadBlockedHosts` have also been added to `bigbluebutton.properties` to allow administrators to define what protocols a URL must use and to explicitly define hosts that a presentation cannot be downloaded from. All URLs passed to `insertDocument` must conform to the requirements of the two previously mentioned properties. Additionally, these URLs must resolve to valid addresses,…