Apparently Slack has been saving our password in plain text for a few weeks of 2020, inside the mobile, which could cause other installed applications to read the content.
The error is now fixed, but it is important that you change the password to prevent any malicious app from sharing the password in other places.
Although it sounds very serious, the probability of having an app that is responsible for reading passwords from other apps is relatively low, especially if you are careful with what you install on your mobile, but it can still happen.
Passwords in plain text have been saving from December 21 to January 21, and the problem has been fixed in the latest version of the Play Store (changing the password would not be very useful if you keep the old version on your mobile).
Many of the affected users have received an email with this topic, advising to reset the password from a desktop computer following a series of instructions. If you have the latest version on your mobile you can change the password from there.
The password change option will not be available if our organization uses single sign-on, in which case there is no problem as this error would not affect those accounts.