Illustrator 25.3 breaks extensions
The Illustrator 25.3.0 and Illustrator 25.3.1 updates prevent several extensions to launch and to run properly, such as our extension Fontself Maker.
The CEP team suggested a workaround to bypass the initial blocker issue, but there are additional critical bugs that prevent users to run their tools as expected.
Here is the more detailed bug tracking: https://github.com/Adobe-CEP/CEP-Resources/issues/367
The changes are intended as part of the new CEF update. These are not issues on the CEP side but more security restrictions that came with the new CEF update. The workarounds (https://github.com/Adobe-CEP/CEP-Resources/issues/367) should be good for the plugin developers in the short term, but for the long term, plugin developers should make changes to ensure that they are following the latest web standards for cross-site workflows.
Franz Hoffman commented
A temporary solution has been provided by the CEP team (see the Github issue for technical details), but there is no guarantee this will fix the problems on the long term :(