Is it permissible to own a plot of land that was received as a gift, given that the mayor tried to embezzle it by putting a fake name on it?

If you acquired the land through a legitimate Islamic means, such as an endowment from the ruler or a gift from its owner, then there is no blame upon you for owning it. The attempt by the municipality official to unlawfully seize it holds no weight. It is important to warn against the grave danger of seizing land unjustly, as the Prophet, peace and blessings be upon him, cautioned against it, saying: "Whoever takes a span of land unjustly, will have it tied around his neck from seven earths," and "Whoever usurps a piece of land unjustly will meet Allah while He is angry with him."