A vulnerability exists in Sentry Seer, tracked as CVE-2026-90999, when automated issue remediation is enabled. Sentry is a platform for monitoring software errors and performance. Seer is an automated debugging assistant within Sentry that can generate remediation steps and hand off issues to a coding agent. Attackers can craft malicious events and submit them to Sentry via a public DSN. These events can bypass trust boundaries when Seer is configured to automatically pass issues to a coding agent. Malicious fields within these events are processed by Seer and can be transformed into untrusted instructions for the coding agent. The vulnerable workflow involves Sentry ingesting attacker-generated events that Seer analyzes. Seer uses attacker-controlled fields to generate a root-cause analysis that is embedded in the prompt for the coding agent. The coding agent then interprets this fabricated analysis and may download and execute attacker-controlled packages. This can lead to arbitrary code execution within the coding agent's environment and access to connected source repositories. No patch is currently available, but mitigations include disabling automated remediation or the Seer handoff feature. Restricting coding agent package installation is also a potential mitigation.