For security reasons, if you use the accelerate endpoint provided by OSS to access an object in a bucket for which transfer acceleration is enabled after December 15, 2020, the Content-Disposition:'attachment=filename;' header is added to the response, which means that the object that you access is downloaded as an attachment.

To access the object but not download it as an attachment, you must bind a custom domain name to the bucket in which the object is stored and resolve the custom domain name to the accelerate endpoint provided by OSS. For more information about how to use custom domain names to access OSS, see [Bind accelerate endpoints].
(https://help.aliyun.com/document_detail/145247.html?spm=a2c4g.11186623.2.19.286716935TW33U#task-2347343)

Note: Buckets for which transfer acceleration is enabled before 00:00:00 December 15, 2020 are not affected.