Is being accepted without funding a dangerous sign? Does this means that the faculty doesn't care about you?
Yes and Yes. I've never known a PhD student to be accepted without funding of some sort. Generally, the number of PhDs a department admits is also the number of students the department can cover with RAs/TAs. I have no insider information, but my guess would be the school had a dearth of qualified applicants to the CS Masters program, and gave you one of their slots.
Self funding a PhD puts you at a tremendous dis-advantage, as all the other students are funded to do their research, but you will have to find outside work, and do research "on the side."
Also, consider what incentive your advisor (if you are lucky enough to find one) has to work with you. The prof invested in other PhD students by funding them, he's got skin in the game (so to speak), and incentive to make them succeed. As an unfunded PhD, your priority will be near the bottom of any prof.
I would recommend following one of the two options below
1) Don't accept the unfunded PhD slot and re-apply. Since you were accepted, you may be able to ask why you weren't funded. They may provide suggestions to help you re-apply.
2) Switch to the masters program. Masters students aren't usually funded, so you will be competing with others like you. You will work with the same profs, and will still have a chance to impress them. One of them may fund you.
I've know several Masters student who were employed by a prof after proving themselves in class. Generally, the prof fast-tracked them to the PhD program.