Infisical has raised $40 million in Series B funding at a $600 million valuation, bringing fresh capital to a security problem emerging alongside enterprise AI adoption: how to let software agents work inside critical systems without giving them the credentials that unlock those systems. The round was led by Elad Gil, who also invested in the company's Series A. Other investors include Gradient and Y Combinator. Infisical plans to use the funding to accelerate product development, expand its…