All municipalities which have a certificate of incorporation issued by the Secretary of State and all township governments which have heretofore been established by act of the General Assembly are hereby declared to be perpetual bodies, politic and corporate and are entitled to exercise all the powers and privileges and are subject to all the limitations and liabilities provided for municipal corporations in this State.

The incorporation or corporate capacity of any municipality or township government established heretofore by act of the General Assembly shall not be attacked in any court in this State except as hereinafter provided by statute.