FB9157626 - Preload Top Hit breaks run_at document_start

[lapcat]

If a Safari web extension injected content script has "run_at": "document_start" specified in the extension's manifest.json, the script can fail to run at document start when Safari's "Preload Top Hit" setting is enabled. This bug occurs on both iOS and macOS.

A bug report has been filed with Apple as FB9157626

More details and a sample project are in my blog post: https://lapcatsoftware.com/articles/2021-6-11.html

[xeenon]

This is fixed in WebKit Web Extensions and Safari Technology Preview 192.

[lapcat]

This appears to be fixed in Safari 18.