Etherpad is a real-time collaborative editor. In versions prior to 1.8.16, an attacker can craft an .etherpad file that, when imported, might allow the attacker to gain admin privileges for the Etherpad instance. This, in turn, can be used to install a malicious Etherpad plugin that can execute arbitrary code (including system commands). To gain privileges, the attacker must be able to trigger deletion of express-session state or wait for old express-session state to be cleaned up. Core Etherpad does not delete any express-session state, so the only known attacks require either a plugin that can delete session state or a custom cleanup process (such as a cron job that deletes old sessionstorage: records). The problem has been fixed in version 1.8.16. If users cannot upgrade to 1.8.16 or install patches manually, several workarounds are available. Users may configure their reverse proxies to reject requests to /p//import, which will block all imports, not just .etherpad imports; limit all users to read-only access; and/or prevent the reuse of expresssid cookie values that refer to deleted express-session state. More detailed information and general mitigation strategies may be found in the GitHub Security Advisory.

Directory traversal vulnerability in node/hooks/express/tests.js in Etherpad frontend tests before 1.6.1.

Directory traversal vulnerability in node/utils/Minify.js in Etherpad 1.1.1 through 1.5.2 allows remote attackers to read arbitrary files by leveraging replacement of backslashes with slashes in the path parameter of HTTP API requests.

Directory traversal vulnerability in node/utils/Minify.js in Etherpad 1.1.2 through 1.5.4 allows remote attackers to read arbitrary files with permissions of the user running the service via a .. (dot dot) in the path parameter of HTTP API requests. NOTE: This vulnerability is due to an incomplete fix to CVE-2015-3297.

node/utils/ExportEtherpad.js in Etherpad 1.5.x before 1.5.2 might allow remote attackers to obtain sensitive information by leveraging an improper substring check when exporting a padID.

templates/pad.html in Etherpad-Lite 1.7.5 has XSS when the browser does not encode the path of the URL, as demonstrated by Internet Explorer.

In Etherpad < 1.8.3, a specially crafted URI would raise an unhandled exception in the cache mechanism and cause a denial of service (crash the instance).

Etherpad < 1.8.3 is affected by a missing lock check which could cause a denial of service. Aggressively targeting random pad import endpoints with empty data would flatten all pads due to lack of rate limiting and missing ownership check.

Etherpad <1.8.3 stored passwords used by users insecurely in the database and in log files. This affects every database backend supported by Etherpad.

Etherpad < 1.8.3 is affected by a denial of service in the import functionality. Upload of binary file to the import endpoint would crash the instance.

An Argument Injection issue in the plugin management of Etherpad 1.8.13 allows privileged users to execute arbitrary code on the server by installing plugins from an attacker-controlled source.

A Cross-Site Scripting (XSS) issue in the chat component of Etherpad 1.8.13 allows remote attackers to inject arbitrary JavaScript or HTML by importing a crafted pad.