Firefox may have stored personal Twitter data in its cache

[harlan4096]

Firefox users who use Twitter may get a notification by the service when they connect to the site the next time that informs them that personal data may have been stored inadvertently in the browser's cache.

The message states:

Important information for Firefox users

We recently learned that the way Mozilla Firefox stores cached data from Twitter may have resulted in non-public information being inadvertently stored in the browser's cache. For example, if you downloaded your data using Firefox, the browser may have retained a copy of the download for a period of time. We have made changes to prevent this from happening again.

According to Twitter's notification, personal information such as downloaded data from Twitter or direct message, could have been cached by Firefox. While that is not a problem on a device with a single-user, information could have leaked on devices that are used by multiple users, e.g. on public Internet workstations.

Other users or administrators could find the data if they browsed the cache of the browser. Firefox's default caching period is set to 7 days but it is possible to change the retention in the browser's settings.

Twitter notes that it has made changes so that the data is no longer stored in Firefox's cache. Other browsers, non-Firefox-based browsers, are not affected by the issue according to Twitter. Other Firefox-based browsers may be affected by the issue on the other hand.

It is unclear if Firefox's caching may cause the same issue on other services. Betanews colleague Brian Faglioli asked Mozilla about this on Twitter and received a reply stating that the organization was looking into this.

It is a good practice to clear caches and other data after using public machines to access content on the Internet or work locally on a device. Some public workstations are configured to erase caches automatically when users sign-out. Firefox users may use the shortcut Ctrl-Shift-Del to clear the history of the browser.
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[silversurfer]

What you need to know about Twitter on Firefox

Yesterday Twitter announced that for Firefox users data such as direct messages (DMs) might be left sitting on their computers even if they logged out. In this post I’ll try to help sort out what’s going on here.
 
First, it’s important to understand the risk: what we’re talking about is “cached” data. All web browsers store local copies of data they get from servers so that they can avoid downloading the same data over the internet repeatedly. This makes a huge performance difference because websites are full of large files that change infrequently. Ordinarily this is what you want, but if you share a computer with other people, then they might be able to see that cached data, even if you have logged out of Twitter. It’s important to know that this data is just stored locally, so if you don’t share a computer this isn’t a problem for you. If you do share a computer, you can make sure all of your Twitter data is deleted by following the instructions here. If you do nothing, the data will be automatically deleted after 7 days the next time you run Firefox.
 
Second, why is this just Firefox? The technical details are complicated but the high level is pretty simple: caching is complicated and each browser behaves somewhat differently; with the particular way that Twitter had their site set up, Chrome, Safari, and Edge don’t cache this data but Firefox will. It’s not that we’re right and they’re wrong. It’s just a normal difference in browser behavior. There is a standard way to ensure that data isn’t cached, but until recently Twitter didn’t use it, so they were just dependent on non-standard behavior on some browsers. [....]

Source Mozilla Blog: https://blog.mozilla.org/blog/2020/04/03...n-firefox/