This is kind of confusing, because you can read it two ways: that it'll only embed the *first* front image (but not exclude other types), or that it'll only embed the first front image *exclusively*.

I'm also not sure if it's clear to users what "the first front image" means, because we don't say what order things are downloaded in, but it does make sense in the case of the CAA, so I don't really mind.

I'd be happy with:
* Embed the first front image and nothing else
* Embed exclusively the first front image
* Embed one front image and nothing else

...etc. (I dropped "in tags" because it's already clear from the previous option.)