Slack has become one of the most popular collaboration and internal communication tools used by companies because of its versatility. The platform's API allows users to develop bots that can receive commands or post content from external services directly in Slack channels, making it easy to automate various tasks.
Many developers post the code for their Slack bots -- some of which are small personal projects -- on GitHub, but fail to remove the bots' access tokens. Some developers even include private tokens associated with their own accounts in the code.
Such tokens can provide access to chats, files, private messages, and other sensitive data shared inside the Slack teams where those developers or bots are members.
Researchers from website security firm Detectify found more than 1,500 Slack tokens on GitHub, some of the tokens providing access to teams from payment providers, Internet service providers, schools, advertising agencies, newspapers and health care providers.
Using those tokens, the researchers gained access to Slack teams and found database credentials, sensitive private messages, files containing passwords, and logins to continuous integration platforms and internal services.
"We also concluded from the internal communication inside Slack teams that people tend to be really sloppy with passing credentials in general," the Detectify researchers said in a blog post.
This is not the first time sensitive access tokens were exposed in projects hosted on GitHub. In 2014, one researcher found almost 10,000 access keys for Amazon Web Services and Elastic Compute Cloud left by developers inside publicly accessible code on GitHub.
Other researchers found credentials for back-end databases and services hard-coded in thousands of mobile apps, which can be easily unpacked and inspected.
"Never commit credentials inside code, ever," the Detectify researchers said. "The first thing you should do is to create environment-variables inside a file and ignore that file from the code repository from [the] start."
Slack allows team owners to restrict the creation of apps and custom integrations to only select members, instead of all of them.