The problem is concerning the way the two browsers Opera 9.50 and FireFox 188.8.131.52 handle a .BMP file, as Gynvael Coldwind posted on Vexillium.org.
Breaking it down to the basics, a simple scanner/ harvester site, created by the cyber criminal, can copy the leaked data from Firefox and Opera memory onto a remote server. It does not select and sort what it copies, but rather takes it all in a bundle, but as it sometimes happens, some personal important information is available on your screen. Picture your Internet banking account being copied as a whole. The longer you stay on a site, the more data is leaked to the third, remote site.
Depending on the capacity of the scanner and the rate it has been set to refresh, it will gather a set amount of information per each refresh. Coldwind demonstrated it with heaps of 7650 bytes and using a visible scanner, but if placed in a hidden iframe, it’s almost impossible to find it.
The vulnerability is caused by the BITMAPINFOHEADER field contained in the BMP format named biClrUsed, indicating how many colors the palette has. 0 = 256, any other number is its equivalent. According to Gynvael, both Firefox and Opera allocate to just the ‘right’ amount of memory or forget to nil the allocated palette. Translated into English, if there’s nothing there, it will be a BMP that copies exactly what the screen displays at the moment.
"If the attacker creates a BMP file with biClrUser = 0, and fills it with gradient, from 0 to 255: 00 01 02 03 04 05 ... and so on, the displayed BMP will in fact copy the palette to the screen, which of
course means that it copies the data lying on the heap to the screen," Coldwind says..
Firefox, Opera 9.50, Memory Leak, Information Leak, Vulnerability, Exploit, .BMP