PRIVACY ISSUE
TLS resumption state is shared between non-concurrent and non-overlapping Guest-mode invocations within same normal-mode invocation. This is shown by a second Guest-mode attempting and succeeding TLS resumption from the previous Guest-mode invocation.

This leaks information by allowing anyone able to observe the plaintext TLS handshakes (ISP, network eavesdroppers, destination websites, etc) to correlate that the two sessions are from the same device and potentially the same user.

Closing and reopening Chrome completely clears TLS state.

Incognito-mode is not affected. Incognito-mode invocation do not attempt to resume previous invocation's TLS connections.

VERSION:
Chrome Version: 70.0.3538.67 + stable
Operating System: Ubuntu 18.04.1 LTS w/ all packages up to date
(used to generate reproduction step screenshots)

Chrome Version: 70.0.3538.67 + stable
Operating System: macOS 10.13.6 w/ all software up-to-date

Not tested on Windows (no installations available).

REPRODUCTION STEPS
-- Start Wireshark
-- Open Chrome to normal profile
-- Open Guest Window
-- Navigate to https://www.amazon.com
-- Observe full TLS Handshake
    -- Session ID A
    -- Attachment chrome-window-1__guest-window-1.png
-- Close Guest Window
-- Wait ~1 minute
-- Open Guest Window
-- Navigate to https://www.amazon.com
-- Observe resumed TLS Handshake
    -- Session ID B
    -- Attachment chrome-window-1__guest-window-2.png
-- Close Guest Window
-- Wait ~1 minute
-- Open Guest Window
-- Navigate to https://www.amazon.com
-- Observe resumed TLS Handshake
    -- Session ID B
    -- Attachment chrome-window-1__guest-window-3.png
-- Close Guest Window
-- Close Chrome
-- Wait ~1 minute
-- Open Chrome
-- Open Guest Window
-- Navigate to https://www.amazon.com
-- Observe full TLS Handshake
    -- Session ID C
    -- chrome-window-2__guest-window-1.png

All TLS Client/Server Hellos condensed in TLS-Hellos.png
 

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	chrome-window-1__guest-window-3__redacted.png 71.7 KB View Download

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Deleted: TLS-Hellos__redacted.png 107 KB

	TLS-Hellos__redacted.png 107 KB View Download