Open Social is a Drupal distribution for online communities, which ships with an optional module called Social Embed.
This module allows a website to display embedded content (such as photos or videos) when a user posts a link to that resource, without having to parse the resource directly.
Added URL's were not sufficiently validated which could lead to a DoS via Blind SSRF and/or Application Takeover via Stored XSS.
This vulnerability is mitigated by the fact that social_embed submodule needs to be enabled.