This userscript fixes a very "unintended" behavior on x.com where pressing the Back or Forward buttons on a mouse over sponsored posts can open advertiser links in a new tab without an actual, intentional click.
Some sponsored posts on x.com (for example, ads showing From didit.me) attach click and mouseup handlers that do not properly check which mouse button triggered the event.
As a result, pressing the mouse Back button (button 3) while the pointer is over an ad image or video is treated as a valid click, causing x.com to call window.open() and open the advertiser link in a new tab.