As someone currently on the market, I've had two calls with two separate people from Client Server, they both declined to continue any sort of process with me without me disclosing my current salary. Now as someone who has gone through quite a lot of job searches, I've gathered that the more you share what you're currently on, the more chances you have to stay on either the same or a minimal bump, so because of that I never share what I'm currently on (I would suggest you do the same).
But apparently Client Server will not continue your hiring process without that. I would highly suggest you avoid them at all cost, if they don't want to get you a job without you disclosing such information, that's too bad for them.
So please, never disclose your current salary with recruiters!