In 1.50, any extension that has onDebugDynamicConfigurations in its activation events is immediately activated when opening any project loading VS Code. This did not happen in v1.49.

[2020-10-13 10:37:47.815] [exthost] [info] ExtensionService#_doActivateExtension Dart-Code.dart-code {"startup":false,"extensionId":{"value":"Dart-Code.dart-code","_lower":"dart-code.dart-code"},"activationEvent":"onDebugDynamicConfigurations"}

There's some discussion around this in #96297 / #88230 and my understanding is that they should not be activated so early. This leads to other issues such as language extensions spawning their language servers for every project (whether they should is another issue - but there's no guidance from VS Code on how they should handle this, especially without knowing why they were activated).