Microsoft Office updates in September 2026 introduced a significant bug in Excel, rendering copy and paste functionality inoperative. This issue, confirmed in KB5002914, affects Excel versions 2016 through 2024. Users encounter silent failures when attempting to copy and paste cells, with the copied cells retaining their moving border while the destination remains empty. AutoFill, formula dragging, and number series generation are also impacted.The problem is recoverable for Windows perpetual and volume Office installations. For Office 2016 MSI editions, removing KB5002914 restores normal functionality. Click-to-Run installations of Office 2019, 2021, and 2024 require reverting to a previously known good build, a process facilitated by the Office Deployment Tool. A PowerShell script is available to automate this build reversion for smaller environments.It is crucial to temporarily exclude the problematic update package from re-deployment via patch management systems. This prevents the bug from reappearing after the initial fix. Users should monitor official Microsoft channels for a corrected update and revert the exclusion once a stable patch is available. Verifying the Office build, testing cell dragging, formula copying, and range pasting are essential post-rollback checks. Additionally, confirming that Ctrl+C/Ctrl+V still functions in other applications like Notepad helps isolate the issue to Excel.