WordPress plugins that enhance user experience often expose administrative configuration fields that directly influence frontend rendering. When these fields are not properly sanitized, they can become a serious attack surface. CVE-2026-2687 affects the Reading Progressbar plugin, a lightweight tool that displays a reading progress indicator using an HTML5 <progress> element and JavaScript.
A stored Cross-Site Scripting (XSS) vulnerability was identified in the plugin’s settings panel, allowing an attacker to inject malicious JavaScript that is permanently stored and later executed in visitors’ or administrators’ browsers. This flaw can be leveraged to compromise administrator sessions, inject backdoors, or fully take over affected WordPress sites.
| CVE | CVE-2026-2687 |
| Plugin Version | https://wordpress.org/plugins/reading-progress-bar/ |
| All Time | 70 000 |
| Active installations | 7 000+ |
| Publicly Published | February 20, 2026 |
| Last Updated | February 20, 2026 |
| Researcher | Artyom K. |
| PoC | Yes |
| Exploit | No |
| Reference | https://www.cve.org/CVERecord?id=CVE-2026-2687 https://wpscan.com/vulnerability/af2e1249-2b69-47b6-85aa-9a6b30c51936/ |
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| Logo of the plugin |  |
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Timeline
| February 13, 2025 | Plugin testing and vulnerability detection in the Reading progressbar have been completed |
| February 13, 2025 | I contacted the author of the plugin and provided a vulnerability PoC with a description and recommendations for fixing |
| February 20, 2025 | Registered CVE-2026-2687 |
Discovery of the Vulnerability
The vulnerability was discovered during security testing of the Reading Progressbar plugin configuration options. Specifically, the “Progressbar height (pixels)” setting accepts user input but fails to properly sanitize or validate it before saving and rendering it into the page.
Because this value is later embedded directly into HTML attributes, an attacker with access to the plugin settings can inject arbitrary JavaScript event handlers.
Understanding of XSS attack’s
Stored XSS occurs when malicious input is saved persistently (for example, in the WordPress database) and later rendered to users without proper escaping. Unlike reflected XSS, stored XSS does not require a crafted URL — the payload automatically executes whenever the affected content is loaded.
Exploiting the CSRF Vulnerability
To exploit CVE-2026-2687:
POC:
1. Go to settings in the plugin tab Reading progressbar 2. In the Progressbar height (pixels) field, enter the payload Payload: 123'onmouseover='alert(777)'____
After saving, the payload is stored in the database. When the progress bar is rendered, the injected JavaScript executes upon user interaction, confirming a stored XSS condition.
Recommendations for Improved Security
To mitigate the risks associated with CVE-2026-2687, administrators should immediately update the Reading Progressbar plugin once a patched version becomes available or disable the plugin if no fix exists. All numeric configuration fields such as Progressbar height must be strictly validated as integers using functions like absint() and sanitized before storage. Developers should escape output contextually with esc_attr() or esc_html() when rendering settings into HTML. Implementing a strict Content Security Policy (CSP) can help reduce the impact of injected scripts by blocking inline JavaScript execution. Site owners should limit access to plugin settings to trusted administrators only, regularly audit stored plugin options for unexpected values, and review user roles to prevent unnecessary privilege exposure. WordPress built-in sanitization utilities such as sanitize_text_field(), esc_attr(), and wp_kses() should be consistently applied across all plugin inputs. To prevent this type of attacks, the vendor adopted our recommended prevention methods, focusing on strong input validation and secure output encoding.
By taking proactive measures to address XSS like CVE-2026-2687 WordPress website owners can enhance their security posture and safeguard against potential exploitation. Stay vigilant, stay secure.
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Artyom k.