Unsolicited tab opening on Safari

Hi everyone,

For a couple of days now, on Safari, when opening a tab (eg google.fr), another tab opens right after and is a spam one.

URL is not always the same eg

ttp://securefastmac.space/landings/197/?affid=mzb_287.43754945.1496692787.28.mz b&utm_source=affxe&utm_medium=cpi&utm_ca…

or

ttp://goodmacfaster.club/landings/197/?affid=mzb_199.41941355.1496692637.28.mzb &utm_source=prfl&utm_medium=cpi&utm_camp…

or ttp://www.advancedmactools.com/affxe/1/?x-context=1023bd39aca995b8851d42b09fb 78 9&utm_source=maffxet1mm&utm_campaign=maf…

How can I prevent these tabs to open every single time since this is very annoying? many thanks!