I understand that the following is becoming feasible, or already is:
Find any 2 data (d1 and d2), for which SHA1(d1) = SHA1(d2)
However, it is not entirely clear to me if there is evidence of the feasibility of:
Find d2 for a specific d1, such that SHA1(d1) = SHA1(d2)
My difficulty in understanding the available literature is that I typically see the attack referred to as "seeking collisions" rather than "seeking a collision"; implying that what is being identified is two data that happen to share a SHA-1, rather than finding a datum which shares the same SHA-1 as a specific target datum.
EDIT: My question is partially redundant to, though more specific in purpose than, this question Second pre-image resistance vs Collision resistance