Browsing mumsnet using the chrome browser on an android phone.
Opened a thread "www.mumsnet.com/Talk/_chat/2729635-Im-being-watched-WATCHED" on an "open in new tab" but the new tab opened with a spam advert page of the kind that tries to make you not navigate away. I presume this is an unintended hijack of some kind.
I copied the content of the navigation field in case it is of use to you but it seems to be gibberish.
data:text/html;base64,PCFET0NUWVBFIGh0bWw+PGh0bWw+PGhlYWQ+PG1ldGEgbmFtZT0idmlld3BvcnQiIGNvbnRlbnQ9IndpZHRoPWRldmljZS13aWR0aCwgdXNlci1zY2FsYWJsZT1mYWxzZSwgaW5pdGlhbC1zY2FsZT0xLjAsIG1heGltdW0tc2NhbGU9MS4wIj48L2hlYWQ+PGJvZHk+PGRpdiBpZD0iaWZybSIgc3R5bGU9InBhZGRpbmc6MDsgbWFyZ2luOjA7Ij48aWZyYW1lIHNyYz0iaHR0cHM6Ly9zMy5hbWF6b25hd3MuY29tL25vdGlmaWNhdGlvbmNlbnRlci9pbnRsL3VrLzZzL2V4cC93aW5uZXIuaHRtbCIgc3R5bGU9InRvcDowOyBsZWZ0OjA7IHdpZHRoOjEwMCU7IGhlaWdodDoxMDAlOyBwb3NpdGlvbjogYWJzb2x1dGU7IGJvcmRlcjowIiBzY3JvbGxpbmc9InllcyIgYWxsb3dGdWxsU2NyZWVuPSJ5ZXMiPjwvaWZyYW1lPjwvZGl2PjwvYm9keT48L2h0bWw+
This seems to happen quite regularly - what kind of info will help you to stop it?