Last Modified: Apr 10, 2019
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Known Affected Versions:
11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4
11.6.0, 11.5.1 HF5
Opened: Feb 24, 2014
When WA optimized images to WebP format, the first WebP response for each image is served without a Vary header. The header is present for subsequent responses where the WebP is served from cache.
Omitting the Vary header might allow downstream caches to incorrectly cache and serve WebP content to browsers which do not understand it.
Both Image-optimization and Optimize-for-client enabled in the WA Policy and requests for images from WebP capable browsers behind downstream caches.
The Vary on user-agent header is properly generated whenever WebP content is served.