Authenticated PostHog users vulnerable to SSRF

PostHog provides open-source product analytics, session recording, feature flagging and A/B testing that you can self-host. A server-side request forgery (SSRF), which can only be exploited by authenticated users, was found in Posthog. Posthog did not verify whether a URL was local when enabling webhooks, allowing authenticated users to forge a POST request. This vulnerability has been addressed in `22bd5942` and will be included in subsequent releases. There are no known workarounds for this vulnerability.