Microsoft's September Excel update breaks copy and paste

Microsoft has acknowledged that its September security update for Excel can break copy and paste. In a note added to the support article for KB5002914, dated 8 September 2026, the company says the paste operation might fail silently in Excel 2024, 2021, 2019 and 2016, and that it is still researching the problem.

What Microsoft says goes wrong

The known-issue entry describes a failure with no warning at all. The source content stays selected and the destination is left unmodified even though the user has tried to paste, and nothing signals that anything went wrong - no error message, no beep, no visual cue. Microsoft has not published a workaround, and says it will post more information in the support article when it has it.

Which versions are affected

The note covers Excel 2024, 2021, 2019 and 2016. KB5002914 itself is a security update for Excel 2016 that addresses a remote code execution vulnerability and an information disclosure vulnerability, and Microsoft notes the download-centre package applies to installer-based Office 2016 editions rather than the Click-to-Run builds used by Microsoft 365 subscribers. The paste problem is listed as a known issue in the same update.

For anyone mid-deadline, the practical consequence is that copied data needs to be checked rather than trusted. Until Microsoft ships a fix, the only reliable signal that a paste worked is the result on screen, because the application will not tell you either way.

Our opinion

A silent failure is a worse bug than a crash. A crash announces itself, stops the work and sends people looking for a cause, while a paste that leaves the destination untouched lets a spreadsheet carry on looking correct with the wrong numbers in it. For a tool that underpins forecasting, payroll and audit work, an error that produces no error message is not a minor inconvenience - it is a data integrity problem waiting for someone not to notice.

The wider lesson is about how patching is communicated. Security updates ship on a fixed monthly cadence, and when one introduces a regression the honest fix is a fast, prominent note rather than a line buried among the known issues. Microsoft has documented this one properly; the next step is either a rollback path or a repair update, and speed matters more here than in most patch regressions.