Slack leaked hashed passwords from its servers for years

Users who created shared invitation links for their workspace had login details slip out among encrypted traffic

Did Slack send you a password reset link last week? The company has admitted to accidentally exposing the hashed passwords of workspace users.

The issue occurred when a user created or revoked a shared invitation link for their workspace. The good news is that the password wasn't plaintext, and it wasn't visible in any Slack clients. The bad news is that it could be picked up by monitoring encrypted traffic from Slack's servers, and it appears that all users who created or revoked those links between April 17, 2017, and July 17, 2022, are affected.

Slack said only 0.5 percent of users were affected, which doesn't sound too terrible until you consider how many Slack users are out there. While getting a definitive user figure for any chat platform is tricky and varies depending on what measure the vendor is using, it is safe to assume Slack has 10 million or more daily active users, meaning that at least 50,000 could have been affected. We asked the company to confirm this, and will update if there is a response.

Slack lays claim to over 169,000 paid customers and says "millions of people around the world use Slack to connect their teams."

The company was informed of the issue by an independent security researcher on July 17, and swiftly fixed the issue before assessing the scale of the impact. "We have no reason to believe that anyone was able to obtain plaintext passwords because of this issue," it insisted, but has still reset the passwords of affected users regardless.

It also recommends the inevitable move to two-factor authentication and the use of unique passwords for every service in use.

The problem is that while the passwords were hashed and salted, and Slack noted that "it is practically infeasible for a password to be derived from the hash," extracting a password is possible (the key word is "practically"). Miscreants are well versed in brute-force methods and it has been possible to harvest those passwords for years.

It would therefore also be a good idea to check out the access logs for one's account, just in case, as well as perform the reset as recommended by Slack. ®

Send us news

Nvidia patches 29 GPU driver bugs that could lead to code execution, device takeover

Take a break from the gaming and fix these now

Salesforce ends CEO job share – again. Marc Benioff back as sole boss

Bret Taylor returns to entrepreneurial roots after losing his gig as chair of Twitter

DoJ worries messaging apps could hide evidence of crime, corruption

Record keeping rules might need a tweak to ensure content is preserved

Egad, did Apple do something right? End-to-end encryption for (most) iCloud services

And remember CSAM scanning plan? Forget that was ever a thing

Google says Android runs better when covered in Rust

Banishing memory safety bugs cuts critical vulnerabilities

REvil-hit Medibank to pull plug on IT, shore up defenses

If safety regulations are written in blood, what are security policies written in? Sweat and cursing?

States label TikTok 'a malicious and menacing threat'

Texas bucks app off government devices as Indiana takes social media biz to court

Sirius XM flaw unlocks so-called smart cars thanks to code flaw

Telematics program doesn't just give you music, but a big security flaw

Google warns stolen Android keys used to sign info-stealing malware

OEMs including Samsung, LG and Mediatek named and shamed

Rackspace rocked by ‘security incident’ that has taken out hosted Exchange services

Warns recovery could take several days and pledges better support after customer complaints

FBI warns about Cuba, no, not that one — the ransomware gang

Critical infrastructure attacks ramping up

AWS fixes 'confused deputy' vulnerability in AppSync

Datadog security researchers found the flaw before miscreants did