Site isolation is designed to prevent the theft of passwords or other sensitive data.
https://arstechnica.com/information-technology/2018/07/chrome-enables-site-isolation-to-blunt-the-threat-of-spectre-attacks/
* “Meltdown” and “Spectre”: Every modern processor has unfixable security flaws * new class of vulnerability that came to light in January * same origin policy * blog post published Wednesday * Site Isolation * multi-process architecture * out-of-process iframes * pursuing this for several years * improve the Chrome extension security model * Cross-Origin Read Blocking * Fetch spec * Web developers should check that their resources are served with the right MIME type and with the nosniff response header * this link