It is hardly improper or unethical to try to retrieve as much information as possible from a government-issued document.  If the government released the information then it is no longer withheld from the public.

If the government tried to withhould information but didn't do so effectively, and the information were sent to an attorney that had requested it on behalf of a client, the attorney might be under a duty to inform the government of the error if discovered, and in some cases might be under an obligation not to disclose the inadvertently disclosed and potentially privileged information to the client.  But if the government publicly posts information or provides it to a private party requesting it for its own purposes, or gives it to reporters, and the information includes ineffectively redacted data, it's tough luck for the government.  The data is now public for anyone who wants to figure out how to retrieve it.  Sometimes it is text that's white-against-white.  Sometimes it's text that's there, but covered by a black or white layer.  Or whatever.  Once it's been publicly released , the cat's out of the bag.

Hint:  We own the government.  It doesn't own us.