这个报错其实不影响运行，但有些有强迫症的同学可能会很难受，以下是解决方法：

报错代码：

:deep() {.avatar {width: 178px;height: 178px;display: block;}.el-upload {border: 1px dashed var(--el-border-color);border-radius: 6px;cursor: pointer;position: relative;overflow: hidden;transition: var(--el-transition-duration-fast);}.el-upload:hover {border-color: var(--el-color-primary);}.el-icon.avatar-uploader-icon {font-size: 28px;color: #8c939d;width: 178px;height: 178px;text-align: center;}}

改为：

  :deep(.avatar) {width: 178px;height: 178px;display: block;}:deep(.el-upload) {border: 1px dashed var(--el-border-color);border-radius: 6px;cursor: pointer;position: relative;overflow: hidden;transition: var(--el-transition-duration-fast);}:deep(.el-upload:hover) {border-color: var(--el-color-primary);}:deep(.el-icon.avatar-uploader-icon) {font-size: 28px;color: #8c939d;width: 178px;height: 178px;text-align: center;}

具体原因见：Vue3 样式穿透。