Why does Iphone add characters /m1b3f0rm to the frem address?

Question

iPhone

Faced with an amazing problem: Safari on Iphone adds the characters /m1b3f0rm to the src of the frame, for example,
the address src="some_file.html" turns into src="some_file.html/m1b3f0rm". If you specify the full URL http://..., then there is no error.
A Google search for the combination m1b3f0rm gave 10700 matches, and two days ago there were 5700 of them. Basically, these are mentions in the site logs, i.e. the problem is not only with us.
Surprisingly, on two iPhones with the same version of iOS, in one case there is a problem, but not in the other. The same problem is observed on iPhones with different versions of iOS. Also a month ago on the same iPhone with the same iOS, there was no error on the same site.
those. It can be assumed that the problem is in some kind of software.
So far, we have found such a workaround: the src frame is not specified at all, and then after loading the page, add it with a script.
Maybe someone knows what it is?

Answer 1

Beacon. Spy.