added cache file question

Hi,
your plugin has informed me of some file changes, as follows
wp-content/cache/all/can-you-buy-permethrin-crea/index.html
wp-content/cache/all/accutane-uk.pdf/index.html
there are others.
I know these are cached files, should I be concerned?
my site is up to date, Jetpack is protecting, Akismet is on, I themes is installed, graviytscan is scanning for malware.
Or is this a cache plugin issue?
can you help?
thanks

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