PowSyBl Core allows deserialization of untrusted SparseMatrix data

PowSyBl (Power System Blocks) is a framework to build power system oriented software. In versions 6.3.0 to 6.7.1, there is a deserialization issue in the read method of the SparseMatrix class that can lead to a wide range of privilege escalations depending on the circumstances. This method takes in an InputStream and returns a SparseMatrix object. This issue has been patched in com.powsybl:powsybl-math: 6.7.2. A workaround for this issue involves not using SparseMatrix deserialization (SparseMatrix.read(...) methods).