CVE-2025-53563 is a high-severity reflected Cross-site Scripting (XSS) vulnerability identified in the LambertGroup Youtube Vimeo Video Player and Slider plugin, affecting versions up to 3.8. The vulnerability arises from improper neutralization of user-supplied input during web page generation, classified under CWE-79. Specifically, the plugin fails to adequately sanitize or encode input parameters that are reflected in the web page output, allowing an attacker to inject malicious scripts. When a victim visits a crafted URL containing the malicious payload, the injected script executes in the context of the victim's browser. This can lead to theft of session cookies, redirection to malicious sites, or execution of arbitrary actions on behalf of the user. The CVSS v3.1 base score is 7.1, indicating a high severity level. The vector string (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L) shows that the attack can be performed remotely over the network without privileges, requires low attack complexity, no privileges, but does require user interaction (clicking a malicious link). The scope is changed, meaning the vulnerability can affect resources beyond the vulnerable component. Confidentiality, integrity, and availability impacts are all low to low-medium but combined justify the high score. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability is particularly relevant for websites using this plugin to embed Youtube and Vimeo videos with slider functionality, which may be common in content-heavy or media-centric sites.

For European organizations, this vulnerability poses a significant risk especially to those operating websites that utilize the LambertGroup Youtube Vimeo Video Player and Slider plugin. Successful exploitation can lead to session hijacking, unauthorized actions on behalf of users, and potential data leakage. This can damage user trust, lead to regulatory non-compliance under GDPR due to data exposure, and cause reputational harm. Organizations in sectors such as media, e-commerce, education, and government that rely on embedded video content are particularly at risk. Since the attack requires user interaction, phishing campaigns targeting employees or customers could leverage this vulnerability to escalate attacks. The reflected nature of the XSS means that attackers can craft malicious URLs distributed via email or social media, increasing the attack surface. Additionally, the changed scope impact suggests that the vulnerability could be leveraged to affect other components or user sessions beyond the immediate plugin context, amplifying potential damage.

1. Immediate mitigation should include disabling or removing the LambertGroup Youtube Vimeo Video Player and Slider plugin until a patch is available. 2. Implement Web Application Firewall (WAF) rules to detect and block common XSS payloads targeting the plugin's parameters. 3. Employ Content Security Policy (CSP) headers to restrict script execution sources, mitigating the impact of injected scripts. 4. Conduct thorough input validation and output encoding on all user-controllable inputs related to video embedding and sliders. 5. Educate users and administrators about the risks of clicking untrusted links, especially those leading to the affected web pages. 6. Monitor web server logs for suspicious URL patterns indicative of attempted exploitation. 7. Once a vendor patch is released, prioritize prompt testing and deployment. 8. Review and update incident response plans to include handling of XSS incidents and potential data breaches stemming from this vulnerability.