signal app icon 3Signal's Mac app displays recently received messages in the Notification Center on macOS, and this feature could compromise a user's disappearing private messages, as discovered by security researcher Alec Muffett and reported by Motherboard.

One of Signal's main advantages is its ability to send disappearing messages, so that after a predetermined amount of time the message is deleted from the app.

Muffett pointed out on Twitter this week that Signal's default Mac app settings somewhat defy this security measure due to the way Macs handle notifications. So, even if you send a self-destructing message within the Signal app, the messages remain on the recipient's Mac Notification Center, displaying your name and message details. Muffett was running macOS 10.13.4 and Signal version 1.9.0.

signal app notifications

Mac security researcher Patrick Wardle then investigated the issue further, discovering that the "deleted" Signal messages that remain in the Notification Center are saved on the Mac's disk inside the operating system. While this is true of any app that displays notifications, it's particularly troublesome for Signal users in need of high-level security, like government workers or journalists.

Any malicious third parties would still need to get their hands on your Mac to get into your message history, so as Motherboard pointed out, "this is not a major threat for most people." Still, this could be a major security risk for high-level Signal users, since this means that any disappearing messages that popped up in Notification Center can be recovered later, "even after they are gone within the Signal app."

Wardle summed up his findings:

In short, anything that gets displayed as a notification (yes, including 'disappearing' Signal messages) in the macOS Notification Center, is recorded by the OS.

If the application wants the item to be removed from the Notification Center, it must ensure that the alert is dismissed by the user or programmatically! However, it is not clear that this also 'expunges' the notifications (and the their contents) from the notification database...i'm guessing not! If this is the case, Signal may have to avoid generating notifications (containing the message body) for disappearing messages...

Wardle said that Signal's iOS app does not appear to have a similar issue at this time, although the app "should be investigated." Of course, any Signal Mac user who is worried about potential privacy risks can navigate to Signal's Preferences menu on the top-left corner of the screen when the app is open, click Notifications, and "Disable notifications."

Tag: Signal

Top Rated Comments

497902 Avatar
39 months ago
Lol, right. I wouldn’t trust any of these supposedly secure messaging systems. Just because they haven’t discovered an exploit yet, doesn’t mean its not there and being exploited. Turning off features to patch of security holes after they’ve been made public isn’t going to do you much good at all.
Feel free to check the source code yourself then if you doubt it.
Score: 4 Votes (Like | Disagree)
497902 Avatar
39 months ago
In short: Disable this feature, problem solved.
Score: 3 Votes (Like | Disagree)
C DM Avatar
39 months ago
99.999% of the time, no point whatsoever.

Either the content is not worth encoding or it is being monitored by people more sophisticated in breaking the cypher than you are at encoding it. The "one time pad" is still the only unbreakable encryption method but, since it relies upon distributing multiple copies of the pad (to the sender and recipient(s)), it isn't secure either.
Well, sounds like there isn't a point to locks either since someone somewhere can certainly pick whatever one you might use.
Score: 1 Votes (Like | Disagree)
twistedpixel8 Avatar
39 months ago
This is ridiculous. You need to assume that anything you send to someone has been read and potentially recorded. These "disappearing messages" are misleading and anyone who takes them for temporary is simply naive.
Score: 1 Votes (Like | Disagree)
alexander258954 Avatar
39 months ago
I find it hilarious that someone can have the capacity and understanding of macOS to create a macOS app but somehow still doesn't understand that notifications are stored infinitely in Notification Center until the user manually clears them out. Hilarious but also annoying. Please Apple can we please please stop with the paper trails? I will never stop clearing (force quitting) my recent iOS apps and obsessively clearing Notification Center. They should auto-clear out after about an hour in my opinion. I don't care about the wallpaper I downloaded, decided I didn't like, and deleted a month ago. What is the point in showing me a notification from a month ago?

Edit: If you disable the notifications for an app they're just hidden but if you re-enable them in Sys Prefs all the old notifications come back. They don't go anywhere. How great is that :) :) :) :) :) :) :)
Score: 1 Votes (Like | Disagree)
Kaibelf Avatar
39 months ago
Honestly if you are getting a message that is compromising you likely don’t want t popping up as a banner on a larger screen than necessary anyway.
Score: 1 Votes (Like | Disagree)

Top Stories

tracking disabled ios 14 5

Analytics Suggest 96% of Users Leave App Tracking Disabled in iOS 14.5

Friday May 7, 2021 1:51 am PDT by
An early look at an ongoing analysis of Apple's App Tracking Transparency suggests that the vast majority of iPhone users are leaving app tracking disabled since the feature went live on April 26 with the release of iOS 14.5. According to the latest data from analytics firm Flurry, just 4% of iPhone users in the U.S. have actively chosen to opt into app tracking after updating their device...
macbook colors 3d black bezels

Prosser: Next MacBook Air Could Come in Colors Similar to iMac

Friday May 7, 2021 6:55 am PDT by
According to Apple leaker Jon Prosser, Apple's upcoming release of the MacBook Air will feature various colors, similar to the colors in the newly released 24-inch iMac. In the latest video of his YouTube channel Front Page Tech, Prosser says the same source who accurately provided him information on the first Apple silicon iMac coming in colors has told him that he recently saw a prototype...
snapchat dark mode

Snapchat Rolls Out Dark Mode on iOS

Wednesday May 5, 2021 1:17 am PDT by
Nearly two years following the release of iOS and iPadOS 13, which included native, built-in, and systemwide dark mode, Snapchat, one of the world's most prominent social media networks, has finally rolled out a dark mode theme for iOS users. Snapchat began testing a dark mode theme of its app design late last year with a small group of iOS users. Now, Snapchat says that as of this week, it...
tile amazon sidewalk integration

Tile to Leverage Amazon Echo and Ring Devices to Better Compete With AirTags

Friday May 7, 2021 2:07 pm PDT by
Amazon today announced that it is teaming up with Tile to add Amazon Sidewalk integration to Tile's Bluetooth trackers. Amazon Sidewalk, for those unfamiliar, is a network of Amazon Bluetooth devices that's designed to improve the connectivity of devices like the Ring and Amazon Echo. Tile will now be joining Amazon Sidewalk, and through this integration, Amazon Echo and Ring devices will be ...
tile sticker e1570533758981

Tile CEO: 'We Welcome Competition From Apple, But We Think It Needs to Be Fair'

Tuesday May 4, 2021 9:51 am PDT by
Just after Apple announced its AirTags, Tile CEO CJ Prober relayed his concerns about competing with Apple in the tracking space, and said that Tile would ask Congress to investigate Apple's business practices specific to Find My and item trackers. Prober this week did an interview with Bloomberg, where he further expanded on Tile's complaints about Apple and why he feels that Tile is...
airtag 1

AirTag Anti-Stalking Measures 'Just Aren't Sufficient' Says Washington Post Report

Wednesday May 5, 2021 6:03 pm PDT by
The safeguards that Apple built into AirTags to prevent them from being used to track someone "just aren't sufficient," The Washington Post's Geoffrey Fowler said today in a report investigating how AirTags can be used for covert stalking. Fowler planted an AirTag on himself and teamed up with a colleague to be pretend stalked, and he came to the conclusion that the AirTags are a "new means...
signal instagram ads3

Signal Shares the Instagram Ads Facebook Doesn't Want You to See

Wednesday May 5, 2021 1:29 am PDT by
Encrypted messaging app Signal has had a series of Instagram ads blocked from the social media platform, after it attempted to show users how much data the Facebook-owned company collects about them and how it's used to push targeted ads. In a blog post, Signal described how it generated the ads to show users why they were seeing them, simply by declaring upfront the information that the...
fortnite apple logo 2

Epic CEO Tim Sweeney Admits App Store's 30% Cut Is Similar to Consoles, Would Have Accepted Special Deal With Apple

Tuesday May 4, 2021 1:54 pm PDT by
Apple's legal battle with Epic Games is continuing on, and during the second day of the trial, Epic Games' CEO Tim Sweeney continued his testimony against Apple. Sweeney was grilled by Apple's lawyers, and made several points seemingly favorable to Apple. In addition to mentioning how he prefers Apple's iPhone and values Apple's privacy policies that he's aiming to dismantle, Sweeney...
iphone 12 preorder purple

Apple Begins Transition to Randomized Serial Numbers With Purple iPhone 12

Wednesday May 5, 2021 9:17 am PDT by
MacRumors previously reported about Apple's plan to switch to randomized serial numbers for future products starting in early 2021, and this transition has now started with the new purple iPhone 12 model in multiple countries. With assistance from Aaron Zollo, host of the YouTube channel ZolloTech, we can confirm that the purple iPhone 12 released last month has a new 10-character serial...
precision finding developer mode

AirTag Precision Finding Interface Includes Hidden 'Developer Mode'

Thursday May 6, 2021 1:32 am PDT by
A frustrated AirTag owner has inadvertently discovered the existence of a hidden "developer mode" in the on-screen interface that Find My displays when the Precision Finding feature is activated to help locate one of Apple's item trackers. Precision Finding is a feature that provides users with specific on-screen directions for finding a nearby AirTag. iPhones with a U1 chip, which includes ...