The word "blanket endorsement" is basically an insurance term, the definition of which is "...instead of scheduling a list of individual items, a single blanket endorsement will cover a wide range of personal belonings. It 'blankets' its coverage over what your carrier offers to cover: jewelry, golf clubs, art etc." The Japanese word for "blanket endorsement" would be "包括契約”.
However, other meanings have derived from this concept. "Blanket endorsement"= cover and insure what the coverer offers to cover.
Here you are saying that it is established that some specific product can guarantee(insure/cover) quality for specific purposes although it may not for other purposes and that the company giving explanation of the product does not intend to tell people that the product is recommendable in its entirety.
ポイント：　筆者は、ここで取り上げられている潤滑剤が使用目的によっては具体的に効果や効能が実証されているということを説明しようとしているのであって、特定の会社の商品を推奨あるいは宣伝しようとしているわけではないということ。

I hope I did not confuse you.
You can get hints from the following sites.

http://www.4insurance.com/homes/endorsements.asp#earthquake
http://www.petitiononline.com/notowar/petition.html
http://www.mainichi.co.jp/eye/feature/401k/200110/03-01.html
http://www.mainichi.co.jp/eye/feature/401k/200110/03-01.html
http://www.elvish.org/resources.html