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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-48821

MEDIUM · 5.8 CVSS v3.1 Published 2026-06-17
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
58/100
Remediation priority · Elevated

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Shaarli is a personal bookmarking service. Versions 0.16.1 and prior contain a DOM-based Cross-Site Scripting (XSS) vulnerability in the Thumbnail Synchronizer feature. When an administrator runs the thumbnail update process, malicious bookmark titles are returned via an AJAX response and inserted into the DOM using innerHTML without proper sanitization. The issue originates from the interaction between the backend thumbnail update endpoint and the frontend JavaScript responsible for rendering update progress. On the backend, the ThumbnailsController::ajaxUpdate method returns bookmark data formatted using the 'raw' formatter. This includes the unescaped bookmark title in the JSON response. On the client side, the script thumbnails-update.js processes this AJAX response and dynamically updates the progress interface. Administrators using the thumbnail synchronization feature are affected and exploitation could lead to session hijacking, privilege escalation, backdoor injection and full compromise. This issue has been fixed in version 0.16.2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Shaarli versions 0.16.1 and prior contain a DOM-based XSS vulnerability in the Thumbnail Synchronizer feature. The backend ThumbnailsController::ajaxUpdate method returns bookmark titles using a 'raw' formatter that does not escape HTML entities. The frontend thumbnails-update.js then uses innerHTML to insert these titles into the DOM without sanitization, allowing injected malicious scripts to execute in the administrator's browser.

MitigationUpgrade Shaarli to version 0.16.2 or later. The fix changes the backend formatter to escape output and/or modifies the frontend to use textContent instead of innerHTML.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS:3.1/AV:L/AC:L/PR:H/UI:R/S:U/C:H/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Shaarli version
    Locate the version file or header in your Shaarli installation (commonly in a VERSION, version.php, or the main index.php header). Compare the version number to 0.16.1 - versions 0.16.1 and prior are affected.
    Affected if Installed version is 0.16.1 or lower (e.g., 0.16.0, 0.15.0, etc.)
  2. Confirm Thumbnail Synchronizer feature is enabled
    Check your Shaarli configuration (data/config.php or admin settings) for the Thumbnail Synchronizer option. This feature must be enabled for the XSS to be triggerable.
    Affected if Thumbnail Synchronizer is turned on in the configuration.
  3. Locate the vulnerable ThumbnailsController
    In the Shaarli source code, find the file containing ThumbnailsController::ajaxUpdate method. Look for the use of a 'raw' formatter when returning bookmark titles.
    Affected if The ajaxUpdate method uses a 'raw' formatter that does not escape HTML entities.
  4. Check frontend thumbnails-update.js
    Find thumbnails-update.js in the static/js directory. Verify it uses innerHTML to insert bookmark titles returned from the backend.
    Affected if The file uses innerHTML (rather than textContent) to render titles from the ajaxUpdate response.
  5. Verify the attack vector is accessible
    Determine if an attacker can add or modify bookmark titles with malicious HTML/JavaScript and trigger the Thumbnail Synchronizer to process them.
    Affected if An attacker can inject malicious script tags into bookmark titles that get processed by the synchronizer.

You are affected if running Shaarli version 0.16.1 or prior AND the Thumbnail Synchronizer feature is enabled, with the vulnerable code paths present in ThumbnailsController and thumbnails-update.js.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Shaarli to version 0.16.2 or later. The fix changes the backend formatter to escape output and/or modifies the frontend to use textContent instead of innerHTML.

Recommended fix High confidence

0.16.2

  1. Back up your existing Shaarli installation and database before proceeding
  2. Download Shaarli version 0.16.2 from the official GitHub repository
  3. Replace the existing Shaarli files with the new version 0.16.2 files
  4. Verify the installation is functioning correctly after the upgrade
  5. Test the Thumbnail Synchronizer feature to confirm the XSS vulnerability is resolved

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-48821 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data