Thumbnails look bad after changing thumbnail size and rebuilding thumbnails

[Kirby]

Affected version

2.3.0 Beta 3

Steps to Reproduce

1. Set thumbnail size to 150 pixel
2. Upload a quadratic image attachment with at least 600x600 pixel
3. Set thumbnail size to 600 pixel
4. Rebuild thumbnails
5. Re-visit the page with the content created in step 2 without doing a hard refresh

Expected Result
The thumbnail image is now 600x600 Pixel and displayed width width and heigth set to 600 pixel pixel showing a crisp image

Actual Result
The thumbnail image is loaded from brwoser cache and still has 150x150 pixel but is now displayed with width and height set to 600 pixel showing a blurry / pixelated image due to upscaling

Suggested Fix
Add a cache buster query string