by Eleanor Wright
• Jun 5 2024
Slack integrations such as webhook APIs are often used to alert on user actions to internal teams. A vulnerability was noted when user supplied data containing a large amount of white space was included in a request to the Slack webhook API. By including enough white space in this data, the messages would be split and truncated. As a result, the malicious payload after the whitespace would appear as a standalone message from the Slack bot. An attacker could exploit this to forge messages containing Slack message markup to perform social engineering and other attacks if an integration, such as a website or other software, included unvalidated user input in the message to the Slack webhook.