Duplicate Cart issue 1.6.x

[LucaR]

If accessing the website while not logged in, ie a Guest account, the cart will show as empty, however, upon clicking on the cart, the cart page will load, and display the most recently updated cart of another user, whether it was made by a guest, or logged in user. Attempting to checkout will display the error "there are no items in the cart"

To reproduce the bug:

We loaded the website, and (as a logged in user or not logged in) added an item to our cart. On another device, NOT logged in, cart shows as empty from the website home page, but upon clicking the cart icon, it will show the previously added item.

This does not happen if:

1. Both users are logged in.

2. The the second user (receiver of the incorrect cart) manually adds an item to the cart, causing the cart icon to update and show "(1) item in cart"

Factors that do not affect the outcome:

1. Browser

2. IP / Internet Connection

 

Attempted to fix (to no avail):

1. Moving backup to different server, to eliminate if it was a server issue

2. Cleaned the database using built in PS cleaner module

3. Disabled all third party modules

4. Disabled custom theme (back to stock theme)

5. Upgraded to 1.6.1.20 from 1.6.1.17

 

Tthe issue seems to be that when a guest user comes on to the site, prestashop does not create a new cart for them from the ps_cart table

but instead fetches the last cart.

[Ramb0t]

We solved this issue by disabling the Mailchimp integration module (Prestashop official) v1.1.4

Not sure exactly the cause but this module was allowing the incorrect cart to be loaded for a user and preventing new guest carts from being created