Description

Privilege escalation in the Downloads API component. This vulnerability was fixed in Firefox 154 and Firefox ESR 153.1.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-08-18T13:17:31.817Z",
  "pubdate": "2026-08-18T13:17:31.817Z",
  "executiveSummary": "This security analysis details a privilege escalation vulnerability residing within the Downloads API component of the affected products. The vulnerability permits an attacker to elevate privileges through improper handling or enforcement of access controls and operational constraints within the application logic of the specified API. Successful exploitation of this flaw could enable a malicious actor to bypass security boundaries, potentially executing unauthorized operations or gaining elevated privileges within the context of the running application. The scope of impact encompasses the client-side integrity and operational security of the host browser environment. Systems affected by this vulnerability include Firefox prior to version 154 and Firefox ESR prior to version 153.1. Mitigation of this risk necessitates applying the vendor-supplied software updates to the fixed versions. The risk implications are significant as unauthorized privilege elevation often serves as a foundational step for broader system compromise or arbitrary code execution cascades depending on the underlying OS integration and auxiliary permissions granted to the browser process.",
  "technicalDetails": "The vulnerability is classified as a privilege escalation flaw localized specifically within the Downloads API component of the browser architecture. The root cause stems from insufficient validation, flawed trust boundaries, or improper capability checks when processing download-related actions or interacting with internal browser interfaces exposed via the API. Attack flow typically initiates when a malicious actor interacts with or abuses exposed methods within the Downloads API, coercing the component into performing operations outside its intended security context or granting higher privileges than authorized. Because the vulnerability exists within an API handling file management and download states, improper state management or insecure inter-process communication mechanisms may allow an attacker to manipulate file system interactions or internal state variables. Exploitation does not inherently require pre-existing elevated privileges on the host system, but relies on the execution context of the browser and the specific exposure parameters of the vulnerable API endpoints. Network exposure depends on how the API is accessed, but web-based vectors such as malicious scripts hosted on compromised or specially crafted web pages can potentially invoke the vulnerable component if proper origin checks and permission models fail. Post-exploitation impact includes the ability to execute unauthorized functional logic, manipulate downloaded assets in restricted locations, or leverage the escalated privilege state to facilitate subsequent attacks targeting the underlying operating system or user profile data. Affected versions include Firefox versions prior to 154 and Firefox ESR versions prior to 153.1, where the API logic fails to adequately enforce security invariants."
}