You are at risk of porn pop-ups and various other undesirable adverts and I assume the viruses that usually go with.
I started a thread about it in Site Stuff [http://www.mumsnet.com/Talk/site_stuff/2685989-Livid-porn-on-my-phone-please-help? here but I know lots of users don't look at the Site Stuff topic.
I did ask HQ to post a warning, but they have not done so, and this has been an ongoing problem for several days.