If you run Excel 2016, 2019, 2021 or 2024 on Windows and installed this month’s Office updates, check any workbook you have edited since 8 September before you trust what is in it. Paste can fail without telling you. The update behind it is Microsoft‘s own September security patch for Excel, KB5002914.
KB5002914 shipped on 8 September as part of the September 2026 Patch Tuesday, and it closes remote code execution and information disclosure flaws in Excel. Reports of broken copy and paste appeared the next day on Reddit and in the Microsoft Q&A forums. On 10 September, Microsoft added the bug to the known issues section of the update’s own support page.
The description there is short. Across Excel 2024, 2021, 2019 and 2016, a paste “might fail silently”. The cells you copied stay outlined, the target cells never change, and Excel says nothing at all. That is what makes this worse than an ordinary bug. An error interrupts you; silence does not. Copy a block of figures, click into the destination, paste, carry on, save, and nothing has warned you that a column never arrived. The damage is already sitting in the file.
Checking takes five seconds. Copy one filled cell and paste it into an empty one: if the target stays empty while the source stays outlined, you have it.
Which installations are actually affected is not settled. Microsoft’s known issue names four Excel versions, while the same page lists the update as applying to Excel 2016 and offers a download package for classic MSI installations rather than Click-to-Run. BleepingComputer tested Excel 2019 build 19127.20302 on Click-to-Run and could not reproduce the failure. Microsoft 365 has not been listed as affected. Users also report that AutoFill and dragging formulas across cells stop working, which Microsoft has not confirmed, and the company has said nothing about what caused any of it.
As of its last revision on 10 September, the support page says only that Microsoft is researching the issue. There is no corrected build and no date for one.
How to get paste working again
Start with your installation type, because the two routes are nothing alike. In Excel, open File, then Account, then About Excel. If that version block says Click to Run, you have Click-to-Run.
One circulating fix is worth skipping. Leaving the update in place and swapping excel.exe for an older copy of the file leaves mismatched files inside a patched Office install, which is a stability and security problem of its own.
Rolling back a security update means giving up fixes for remote code execution flaws, so treat any rollback as temporary and reinstall the patch once a corrected build exists. The known issues section of that support page is where it will show up first, and our Productivity & Business coverage will carry it when it does. Until then, anything important you paste deserves a second look before you save.
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