topics/xz-5.8.4.toml: correct vulnerability type and severity

Suggested-by: Neko205 <neko200553@gmail.com>

Author: MingcongBai

topics/xz-5.8.4.toml

@@ -5,8 +5,8 @@ must_match_all = false
 default = "XZ 5.8.4"
 
 [caution]
-default = "Fixes an invalid memory access vulnerability in liblzma decoder functions - GHSA-5qpq-xqfv-j9pg (CVE pending)"
-zh_CN = "修复 liblzma 解码器函数中一处无效内存访问漏洞，漏洞编号 GHSA-5qpq-xqfv-j9pg（CVE 编号待定）"
+default = "Fixes a Use-After-Free vulnerability in liblzma's decoder functions - GHSA-5qpq-xqfv-j9pg (CVE pending, Severity: High)"
+zh_CN = "修复 liblzma 解码器函数中的一个释放后使用 (use-after-free) 漏洞，漏洞编号 GHSA-5qpq-xqfv-j9pg（CVE 编号待定，严重性：高）"
 
 [packages-v2]
 "xz" = "< 5.8.4"