In case you use one of the Amasty extensions, e.g. Amasty Layered navigation, you may face the issue of the broken blog featured images after the upload.
We have found the issue in Amasty_Shopby extensions, that breaks some other extensions using image upload functionality, including our Magento 2 Blog Extension.
Amasty_Shopby in this file:
adds the plugin to Magento\Catalog\Model\ImageUploader model.
Judging from the code in the following file:
it looks like some fix Amasty added for Magento 2.3.4. and the issue lies in the plugin beforeMoveFileFromTmp.
The original Magento MoveFileFromTmp