Currently, there is no direct method within ChatGPT to sign out of all sessions simultaneously across multiple devices. Users have reported that changing the password might help log out from other sessions, but this is not a guaranteed solution. If you're experiencing account security concerns, the recommended action is to contact OpenAI's help through the help.openai.com messages chatbot to report the issue and request assistance in logging out of all sessions.
If you've signed in using Google, you can try to log out of all Google-connected devices by visiting security.google.com. However, this may not affect sessions where you've logged in directly with your OpenAI credentials.
Please note that the information provided is accurate as of April 28, 2024, based on the search results available. If there have been updates to ChatGPT's features, they may not be reflected in this response.