There's a lot of insane conspiracy theories out there, but it is true that Masonic lodges have been involved in various plots in the last 3 centuries.
Two relatively recent ones that are heavily supported by evidence:
Propaganda Due, that included Silvio Berlusconi carried out multiple terrorist bombing attacks, framing communists for the deaths, and was poised to orchestrate a coup and bring Italy under a renewed fascist dictatorship - https://en.wikipedia.org/wiki/Propaganda_Due
And the Swiss/French/Quebecois suicide cult, Order of the Solar Temple, was founded by rogue masons and incorporated masonic rituals into their weird Templar cult - https://en.wikipedia.org/wiki/Order_of_the_Solar_Temple
In the 1700s/1800s Masonic organisations did plot to overthrow the monarchies of Europe, a noble goal for once. Many of the US founding fathers were Masons. Here in America Masons are weirdly open and public about their events, they seemed a little more covert in the UK.