Microsoft has announced that it will start disabling external workbook links to blocked file types by default between October 2025 and July 2026.

After the rollout, Excel workbooks referencing blocked file types will display a #BLOCKED error or fail to refresh, eliminating security risks associated with accessing unsupported or high-risk file types, including, but not limited to, phishing attacks that utilize workbooks to redirect targets to malicious payloads.

This change is being introduced as a new FileBlockExternalLinks group policy, which expands File Block Settings to include external workbook links.