Jenkins Email Extension Plugin: Attackers able to control email content may specify `file:` URLs for images to read arbitrary files from Jenkins controller filesystem

Jenkins Email Extension Plugin 1933.v45cec755423f and earlier includes a feature that allows inlining images as base64 in email content by setting the data-inline attribute. No restrictions are placed on the image URLs that can be inlined.

This allows attackers able to control the email content to specify file: URLs for images to read arbitrary files from the Jenkins controller filesystem.

The feature allowing inlining images as base64 in email content by setting the data-inline attribute is removed from Email Extension Plugin 1933.1935.v276319e3cc47.