Microsoft's September security update for Excel, intended to address remote code execution vulnerabilities, inadvertently broke the paste function across multiple versions (2016, 2019, 2021, and 2024). The paste operation fails silently without error messages, making the malfunction particularly troublesome for users who receive no indication that their paste action has failed. This represents part of a wider pattern of problematic updates from Microsoft throughout September.

Microsoft has issued a partial hotfix that applies only to Excel 2016, leaving users of newer versions without an immediate solution. The company has further warned that pasting may continue to fail even for those with the fix if workbooks contain conditional formatting. Some users managed to work around the issue using Paste Special, though others were entirely blocked. The broader context reveals September has been particularly difficult for Microsoft's updates generally: the Windows security update required emergency out-of-band fixes, USB audio devices experienced malfunctions, and domain-joined devices encountered additional problems.