There was malware that went undetected for 3 years included in Free Download manager. If you installed it you should read this.
thank you for your replay and welcome to Linux.org.Greetings from the Free Download Manager team. We acknowledge the reports regarding the security concerns and assure you that we're actively investigating their history. As of now, all links on the FDM website are secure and functional. For a comprehensive overview of the situation, we've made an official announcement on our website. We encourage everyone to get more insights here: https://www.freedownloadmanager.org/blog/?p=664
While streaming services have cut down on the amount of downloading most of us have to do nowadays, and built-in browser downloaders can do the job for the casual web surfer, if you’re transferring a serious amount of files on a regular basis then a dedicated download manager is worth a look.
A download manager can prove its worth in dealing with software packages, large image and video files you need to work on, or batches of files that you need to get on your machine. The more downloading you have to do, the better the benefits become—these dedicated tools can boost transfer speeds by splitting files up into chunks or requesting multiple transfers, depending on the source. ( Quoted from GIZMODO WEB SITE)