Prometheus is an open-source monitoring system and time series database. Prior to versions 3.5.3 and 3.11.3, the remote read endpoint (/api/v1/read) does not validate the declared decoded length in a snappy-compressed request body before allocating memory. An unauthenticated attacker can send a small payload that causes a huge heap allocation per request. Under concurrent load this can exhaust available memory and crash the Prometheus process. This issue has been patched in versions 3.5.3 and 3.11.3.
A stored, DOM based, cross-site scripting (XSS) flaw was found in Prometheus before version 2.7.1. An attacker could exploit this by convincing an authenticated user to visit a crafted URL on a Prometheus server, allowing for the execution and persistent storage of arbitrary scripts.