Single word for taking advantage of the situation?

The word closest to that definition is probably opportunist, although historically it has been used in a rather specialised sense.

I feel that the word most closely associated with taking advantage of a situation is exploit which also carries a slightly negative connotation.

Have you considered Exploitative?

exploiting or tending to exploit; especially : unfairly or cynically using another person or group for profit or advantage
"exploitative terms of employment"
"an exploitative film"

Merriam-Webster has its first-known use as 1885.

Capitalise - draw advantages from; "he is capitalizing on her mistake"; "she took advantage of his absence to meet her lover"