What’s Vulnerable › Vulnerabilities

CVE-2025-1521: PostHog slack_incoming_webhook Server-Side Request Forgery Information Disclosure Vulnerability

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-23 · updated 2026-06-17
• Weakness: CWE-918

Description

PostHog slack_incoming_webhook Server-Side Request Forgery Information Disclosure Vulnerability. This vulnerability allows remote attackers to disclose sensitive information on affected installations of PostHog. Authentication is required to exploit this vulnerability. The specific flaw exists within the processing of the slack_incoming_webhook parameter. The issue results from the lack of proper validation of a URI prior to accessing resources. An attacker can leverage this vulnerability to execute code in the context of the service account. Was ZDI-CAN-25352.

Affected products

• PostHog: before 0.3.7 — fixed in 0.3.7

How to fix

Upgrade to a fixed version: PostHog 0.3.7. Check the vendor advisory for mitigations.

References

• https://github.com/PostHog/posthog/commit/6e8f035f9acd339c5ba87ba6ea40fc1ab3053d42
• https://www.zerodayinitiative.com/advisories/ZDI-25-096/

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