CVE-2026-27063 in Kit Plugin
Summary
by MITRE • 10/29/2026
Missing Authorization vulnerability in Kit Kit (formerly ConvertKit) convertkit allows Exploiting Incorrectly Configured Access Control Security Levels.This issue affects Kit (formerly ConvertKit): from n/a through 3.4.7.
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Analysis
by VulDB Data Team • 10/29/2026
The identified security flaw represents a critical failure in access control mechanisms within the Kit platform, formerly known as ConvertKit, specifically affecting versions ranging from initial releases up to version 3.4.7. This vulnerability is classified under CWE-285, which denotes Improper Authorization, and aligns with MITRE ATT&CK technique T1078, Valid Accounts, where attackers leverage improperly configured access control levels to gain unauthorized privileges. The core technical issue stems from the application's inability to properly verify user permissions before processing sensitive requests or exposing restricted data structures. In a well-architected system, every action that modifies state or retrieves private information must be validated against the authenticated identity of the requester and their assigned role within the organizational hierarchy. However, in this instance, the backend logic fails to enforce these boundaries effectively, allowing an actor with lower privileges to perform actions reserved for administrators or other elevated roles without triggering appropriate rejection responses.
From a technical perspective, this misconfiguration typically manifests through insecure direct object references or broken access control on API endpoints that handle user management, subscription settings, or content distribution lists. An attacker who has obtained valid credentials for a standard subscriber account can manipulate request parameters to interact with administrative functions intended only for platform owners or high-level editors. This could involve modifying the configuration of email campaigns, accessing personal data belonging to other users, or altering billing information associated with premium features. The absence of server-side validation means that client-side restrictions are easily bypassed by intercepting and replaying HTTP requests with modified identifiers or role indicators. Such flaws are particularly dangerous because they do not require complex exploitation chains; instead, they rely on the fundamental assumption that authentication alone is sufficient for authorization, which is a common architectural mistake in rapidly developed web applications.
The operational impact of this vulnerability is severe, as it compromises both confidentiality and integrity within the platform ecosystem. For individual users, it poses a significant risk to personal data privacy, potentially exposing email addresses, payment details, or communication history stored by their contacts. For enterprise customers utilizing Kit for marketing automation, the breach could lead to unauthorized changes in campaign strategies, leading to reputational damage and loss of customer trust if inappropriate content is sent out under their brand identity. Furthermore, because access control failures often serve as a foothold for further attacks, this vulnerability can facilitate lateral movement within an organization’s digital infrastructure. An attacker might use the elevated privileges gained through this flaw to exfiltrate bulk data or establish persistent backdoors that remain undetected by standard monitoring tools due to their legitimate-looking origin from authenticated sessions.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary solution is for Kit to release a patched version of the software, specifically updating beyond version 3.4.7, which includes corrected authorization logic that strictly validates user roles against every requested action. Administrators running affected versions should immediately audit their access control policies and ensure that multi-factor authentication is enabled for all administrative accounts to reduce the risk of credential theft leading to exploitation. Additionally, implementing a Web Application Firewall with rules tuned to detect abnormal patterns in API usage can provide an additional layer of defense by blocking requests that attempt to escalate privileges or access unauthorized resources. Long-term resilience requires adopting a principle of least privilege across all application modules and conducting regular security audits focused on identifying broken object level authorization flaws before they are exploited in the wild.