Information Transfer Between Browsers and Tabs

Is it possible for a webpage to detect or otherwise be aware of what other tabs in the same browser, or even other open webpages in other browsers are doing or transmitting?



I am well aware of cookies, and their ability to store information placed by the webdev for local use. This link and this link were also helpful, although I don't particularly like Chrome and I am not just asking about extensions. I am also aware that with a compromised machine or browser anything is possible.



My concern is that with marketing and all the other reasons that promote extensive information gathering (legitimate or otherwise), it may be desirable for a website to try and glean information about any and all usage by reaching outside of its browser's tab, so to speak. With sandboxed tabs, this seems unlikely, but I am sure there are ways around this (if not yet discovered). This would definitely be considered nefarious and possibly illegal for a company to be doing this regularly, but this hasn't stopped many companies from doing all that they can to gain an advantage, or take advantage of users' ignorance. TO BE CLEAR: I am not not referring to full-fledged real-time active hacking of a user's browser. Just data "leakage", so to speak.



Sometimes I am reluctant to do banking in one browser and shopping in another for fear that the central piece of software (the browser) may allow some type of crosstalk. I think this may be unnecessary. If this is not possible, please describe what safeguards are in place within the browser in addition to sandboxing. I am looking for software level details if possible, or anything else that is relevant in addition to the links I posted above... but didn't want to post this on another SE site such as the StackO. Thank you.