Extension could not be loaded because it was not properly signed

When starting Photoshop, you get the following error:

The <extension name> extension could not be loaded because it was not properly signed.

This error message indicates that the installed extension files are not identical to the files created by the software developer.
It could occur due to one of the following reasons:

• Extension files (typically the ones with a JS, JSX, or JSXBIN extension) have been removed or quarantined by the anti-virus software.
• Any unsigned or unexpected files introduced into the folders used by extensions.
  
• The file metadata has been altered because the files were unzipped and subsequently placed on a cloud or network drive.
• The file metadata is incorrect because the files were unzipped using a third-party unzip tool which does not support signed files. 

Install the latest version of Photoshop

Please make sure Photoshop is up-to-date and you are using the latest version.

The current version of Photoshop blocks extensions that are known to be bad.

Solution 1: Reinstall extensions and whitelist any quarantined files

If you use anti-virus software, make sure to whitelist any quarantined files.

Follow the instructions below to reinstall the extensions. 

Solution 2: Uninstall Photoshop and delete folders containing old extensions and extra files

Follow the instructions below to remove all unsigned or unexpected files. Then, follow the instructions in Solution 1 above to reinstall the extensions.